21497591817 has 48 divisors (see below), whose sum is σ = 34320686400. Its totient is φ = 12885298560.

The previous prime is 21497591779. The next prime is 21497591821. The reversal of 21497591817 is 71819579412.

21497591817 is a `hidden beast` number, since 2 + 1 + 49 + 7 + 591 + 8 + 1 + 7 = 666.

It is not a de Polignac number, because 21497591817 - 2²⁷ = 21363374089 is a prime.

It is a super-2 number, since 2×21497591817² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21497591887) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 738142 + ... + 766712.

It is an arithmetic number, because the mean of its divisors is an integer number (715014300).

Almost surely, 2^21497591817 is an apocalyptic number.

It is an amenable number.

21497591817 is a deficient number, since it is larger than the sum of its proper divisors (12823094583).

21497591817 is a wasteful number, since it uses less digits than its factorization.

21497591817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28758 (or 28755 counting only the distinct ones).

The product of its digits is 1270080, while the sum is 54.

The spelling of 21497591817 in words is "twenty-one billion, four hundred ninety-seven million, five hundred ninety-one thousand, eight hundred seventeen".