21681090025 has 45 divisors (see below), whose sum is σ = 31415716293. Its totient is φ = 14842296000.

The previous prime is 21681090007. The next prime is 21681090091. The reversal of 21681090025 is 52009018612.

The square root of 21681090025 is 147245.

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

It can be written as a sum of positive squares in 4 ways, for example, as 1153077849 + 20528012176 = 33957^2 + 143276^2 .

It is not a de Polignac number, because 21681090025 - 2¹⁵ = 21681057257 is a prime.

It is a super-3 number, since 3×21681090025³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 36074725 + ... + 36075325.

Almost surely, 2^21681090025 is an apocalyptic number.

21681090025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21681090025 is the 147245-th square number.

21681090025 is the 73623-rd centered octagonal number.

It is an amenable number.

21681090025 is a deficient number, since it is larger than the sum of its proper divisors (9734626268).

21681090025 is an frugal number, since it uses more digits than its factorization.

21681090025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1240 (or 613 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 34.

The spelling of 21681090025 in words is "twenty-one billion, six hundred eighty-one million, ninety thousand, twenty-five".