21006265640 has 16 divisors (see below), whose sum is σ = 47264097780. Its totient is φ = 8402506240.

The previous prime is 21006265639. The next prime is 21006265661. The reversal of 21006265640 is 4656260012.

It can be written as a sum of positive squares in 2 ways, for example, as 20012629156 + 993636484 = 141466^2 + 31522^2 .

It is a super-2 number, since 2×21006265640² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21006265597 and 21006265606.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 262578281 + ... + 262578360.

Almost surely, 2^21006265640 is an apocalyptic number.

21006265640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21006265640 is an abundant number, since it is smaller than the sum of its proper divisors (26257832140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21006265640 is a wasteful number, since it uses less digits than its factorization.

21006265640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525156652 (or 525156648 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 32.

The spelling of 21006265640 in words is "twenty-one billion, six million, two hundred sixty-five thousand, six hundred forty".