21170087640 has 128 divisors (see below), whose sum is σ = 75995236800. Its totient is φ = 5211095040.

The previous prime is 21170087623. The next prime is 21170087657. The reversal of 21170087640 is 4678007112.

21170087640 is a `hidden beast` number, since 2 + 1 + 1 + 7 + 0 + 0 + 8 + 7 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (21170087623) and next prime (21170087657).

It is a super-2 number, since 2×21170087640² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21170087595 and 21170087604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 739881 + ... + 767960.

Almost surely, 2^21170087640 is an apocalyptic number.

21170087640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21170087640 is an abundant number, since it is smaller than the sum of its proper divisors (54825149160).

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

21170087640 is a wasteful number, since it uses less digits than its factorization.

21170087640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1507874 (or 1507864 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The spelling of 21170087640 in words is "twenty-one billion, one hundred seventy million, eighty-seven thousand, six hundred forty".