21125861257 has 8 divisors (see below), whose sum is σ = 22888758816. Its totient is φ = 19420763712.

The previous prime is 21125861213. The next prime is 21125861287. The reversal of 21125861257 is 75216852112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21125861257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21125861287) 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, 14449243 + ... + 14450704.

It is an arithmetic number, because the mean of its divisors is an integer number (2861094852).

Almost surely, 2^21125861257 is an apocalyptic number.

It is an amenable number.

21125861257 is a deficient number, since it is larger than the sum of its proper divisors (1762897559).

21125861257 is a wasteful number, since it uses less digits than its factorization.

21125861257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28900007.

The product of its digits is 67200, while the sum is 40.

The spelling of 21125861257 in words is "twenty-one billion, one hundred twenty-five million, eight hundred sixty-one thousand, two hundred fifty-seven".