21015552051 has 18 divisors (see below), whose sum is σ = 32870481228. Its totient is φ = 12932646480.

The previous prime is 21015552029. The next prime is 21015552079. The reversal of 21015552051 is 15025551012.

21015552051 is a `hidden beast` number, since 2 + 101 + 5 + 552 + 0 + 5 + 1 = 666.

It is not a de Polignac number, because 21015552051 - 2⁷ = 21015551923 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21015552001) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 6906945 + ... + 6909986.

It is an arithmetic number, because the mean of its divisors is an integer number (1826137846).

Almost surely, 2^21015552051 is an apocalyptic number.

21015552051 is a deficient number, since it is larger than the sum of its proper divisors (11854929177).

21015552051 is a wasteful number, since it uses less digits than its factorization.

21015552051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13816963 (or 13816947 counting only the distinct ones).

The product of its (nonzero) digits is 2500, while the sum is 27.

The spelling of 21015552051 in words is "twenty-one billion, fifteen million, five hundred fifty-two thousand, fifty-one".