21207805641 has 45 divisors (see below), whose sum is σ = 34846382109. Its totient is φ = 12844477800.

The previous prime is 21207805627. The next prime is 21207805649. The reversal of 21207805641 is 14650870212.

The square root of 21207805641 is 145629.

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

21207805641 is a `hidden beast` number, since 2 + 1 + 2 + 0 + 7 + 8 + 0 + 5 + 641 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-21207805641 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21207805596 and 21207805605.

It is not an unprimeable number, because it can be changed into a prime (21207805649) by changing a digit.

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, 14416536 + ... + 14418006.

Almost surely, 2^21207805641 is an apocalyptic number.

21207805641 is the 145629-th square number.

21207805641 is the 72815-th centered octagonal number.

It is an amenable number.

21207805641 is a deficient number, since it is larger than the sum of its proper divisors (13638576468).

21207805641 is an frugal number, since it uses more digits than its factorization.

21207805641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2976 (or 1485 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

Multiplying 21207805641 by its sum of digits (36), we get a square (763481003076 = 873774²).

The spelling of 21207805641 in words is "twenty-one billion, two hundred seven million, eight hundred five thousand, six hundred forty-one".