21278632857 has 16 divisors (see below), whose sum is σ = 28736736000. Its totient is φ = 14003218944.

The previous prime is 21278632831. The next prime is 21278632871. The reversal of 21278632857 is 75823687212.

It is not a de Polignac number, because 21278632857 - 2²⁰ = 21277584281 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21278632877) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2035119 + ... + 2045547.

It is an arithmetic number, because the mean of its divisors is an integer number (1796046000).

Almost surely, 2^21278632857 is an apocalyptic number.

It is an amenable number.

21278632857 is a deficient number, since it is larger than the sum of its proper divisors (7458103143).

21278632857 is a wasteful number, since it uses less digits than its factorization.

21278632857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19120.

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

The spelling of 21278632857 in words is "twenty-one billion, two hundred seventy-eight million, six hundred thirty-two thousand, eight hundred fifty-seven".