51639021 has 24 divisors (see below), whose sum is σ = 85909824. Its totient is φ = 29278080.

The previous prime is 51638989. The next prime is 51639023. The reversal of 51639021 is 12093615.

51639021 is a `hidden beast` number, since 5 + 1 + 639 + 0 + 21 = 666.

It is not a de Polignac number, because 51639021 - 2⁵ = 51638989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51639023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5125 + ... + 11381.

It is an arithmetic number, because the mean of its divisors is an integer number (3579576).

Almost surely, 2^51639021 is an apocalyptic number.

It is an amenable number.

51639021 is a deficient number, since it is larger than the sum of its proper divisors (34270803).

51639021 is a wasteful number, since it uses less digits than its factorization.

51639021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6401 (or 6398 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 51639021 is about 7186.0295713280. The cubic root of 51639021 is about 372.3854182661.

The spelling of 51639021 in words is "fifty-one million, six hundred thirty-nine thousand, twenty-one".