21017750625 has 45 divisors (see below), whose sum is σ = 37956208719. Its totient is φ = 11203668000.

The previous prime is 21017750623. The next prime is 21017750651. The reversal of 21017750625 is 52605771012.

The square root of 21017750625 is 144975.

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

21017750625 is a `hidden beast` number, since 2 + 10 + 17 + 7 + 5 + 0 + 625 = 666.

It can be written as a sum of positive squares in 7 ways, for example, as 12570670161 + 8447080464 = 112119^2 + 91908^2 .

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

It is not a de Polignac number, because 21017750625 - 2¹ = 21017750623 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21017750625.

It is not an unprimeable number, because it can be changed into a prime (21017750623) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 10872159 + ... + 10874091.

Almost surely, 2^21017750625 is an apocalyptic number.

21017750625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21017750625 is the 144975-th square number.

21017750625 is the 72488-th centered octagonal number.

It is an amenable number.

21017750625 is a deficient number, since it is larger than the sum of its proper divisors (16938458094).

21017750625 is an frugal number, since it uses more digits than its factorization.

21017750625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3892 (or 1941 counting only the distinct ones).

The product of its (nonzero) digits is 29400, while the sum is 36.

Multiplying 21017750625 by its sum of digits (36), we get a square (756639022500 = 869850²).

The spelling of 21017750625 in words is "twenty-one billion, seventeen million, seven hundred fifty thousand, six hundred twenty-five".