1821155625 has 45 divisors (see below), whose sum is σ = 3292932643. Its totient is φ = 969576000.

The previous prime is 1821155599. The next prime is 1821155627. The reversal of 1821155625 is 5265511281.

The square root of 1821155625 is 42675.

It is a perfect power (a square), and thus also a powerful number.

1821155625 is a `hidden beast` number, since 1 + 8 + 21 + 1 + 5 + 5 + 625 = 666.

It can be written as a sum of positive squares in 7 ways, for example, as 1788528681 + 32626944 = 42291^2 + 5712^2 .

It is a tau number, because it is divible by the number of its divisors (45).

It is not a de Polignac number, because 1821155625 - 2²¹ = 1819058473 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1821155625.

It is not an unprimeable number, because it can be changed into a prime (1821155627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 3200341 + ... + 3200909.

Almost surely, 2^1821155625 is an apocalyptic number.

1821155625 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1821155625 is the 42675-th square number.

1821155625 is the 21338-th centered octagonal number.

It is an amenable number.

1821155625 is a deficient number, since it is larger than the sum of its proper divisors (1471777018).

1821155625 is an frugal number, since it uses more digits than its factorization.

1821155625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1164 (or 577 counting only the distinct ones).

The product of its digits is 24000, while the sum is 36.

The cubic root of 1821155625 is about 1221.1875083045.

Multiplying 1821155625 by its sum of digits (36), we get a square (65561602500 = 256050²).

The spelling of 1821155625 in words is "one billion, eight hundred twenty-one million, one hundred fifty-five thousand, six hundred twenty-five".