51639990 has 32 divisors (see below), whose sum is σ = 126821376. Its totient is φ = 13450080.

The previous prime is 51639989. The next prime is 51639997. The reversal of 51639990 is 9993615.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51639997) 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, 18726 + ... + 21305.

It is an arithmetic number, because the mean of its divisors is an integer number (3963168).

Almost surely, 2^51639990 is an apocalyptic number.

51639990 is an abundant number, since it is smaller than the sum of its proper divisors (75181386).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51639990 is a wasteful number, since it uses less digits than its factorization.

51639990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40084.

The product of its (nonzero) digits is 65610, while the sum is 42.

The square root of 51639990 is about 7186.0969935007. The cubic root of 51639990 is about 372.3877475074.

The spelling of 51639990 in words is "fifty-one million, six hundred thirty-nine thousand, nine hundred ninety".