21057720551 has 12 divisors (see below), whose sum is σ = 24593322600. Its totient is φ = 17977554000.

The previous prime is 21057720511. The next prime is 21057720569. The reversal of 21057720551 is 15502775012.

It is not a de Polignac number, because 21057720551 - 2⁶ = 21057720487 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057720511) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 843776 + ... + 868373.

It is an arithmetic number, because the mean of its divisors is an integer number (2049443550).

Almost surely, 2^21057720551 is an apocalyptic number.

21057720551 is a deficient number, since it is larger than the sum of its proper divisors (3535602049).

21057720551 is a wasteful number, since it uses less digits than its factorization.

21057720551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1712414 (or 1712407 counting only the distinct ones).

The product of its (nonzero) digits is 24500, while the sum is 35.

The spelling of 21057720551 in words is "twenty-one billion, fifty-seven million, seven hundred twenty thousand, five hundred fifty-one".