21120708657 has 8 divisors (see below), whose sum is σ = 28163611584. Its totient is φ = 14079139088.

The previous prime is 21120708649. The next prime is 21120708683. The reversal of 21120708657 is 75680702112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21120708657 - 2³ = 21120708649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21120708607) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 295773 + ... + 360170.

It is an arithmetic number, because the mean of its divisors is an integer number (3520451448).

Almost surely, 2^21120708657 is an apocalyptic number.

It is an amenable number.

21120708657 is a deficient number, since it is larger than the sum of its proper divisors (7042902927).

21120708657 is a wasteful number, since it uses less digits than its factorization.

21120708657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 666679.

The product of its (nonzero) digits is 47040, while the sum is 39.

The spelling of 21120708657 in words is "twenty-one billion, one hundred twenty million, seven hundred eight thousand, six hundred fifty-seven".