21388057647 has 48 divisors (see below), whose sum is σ = 32132102016. Its totient is φ = 12641112000.

The previous prime is 21388057637. The next prime is 21388057753. The reversal of 21388057647 is 74675088312.

It is not a de Polignac number, because 21388057647 - 2¹⁸ = 21387795503 is a prime.

It is a super-2 number, since 2×21388057647² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21388057647.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388057637) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2452068 + ... + 2460774.

It is an arithmetic number, because the mean of its divisors is an integer number (669418792).

Almost surely, 2^21388057647 is an apocalyptic number.

21388057647 is a deficient number, since it is larger than the sum of its proper divisors (10744044369).

21388057647 is a wasteful number, since it uses less digits than its factorization.

21388057647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8900 (or 8889 counting only the distinct ones).

The product of its (nonzero) digits is 2257920, while the sum is 51.

The spelling of 21388057647 in words is "twenty-one billion, three hundred eighty-eight million, fifty-seven thousand, six hundred forty-seven".