51981138 has 48 divisors (see below), whose sum is σ = 130100256. Its totient is φ = 14824320.

The previous prime is 51981067. The next prime is 51981151. The reversal of 51981138 is 83118915.

51981138 is a `hidden beast` number, since 519 + 8 + 1 + 138 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4356 + ... + 11087.

It is an arithmetic number, because the mean of its divisors is an integer number (2710422).

Almost surely, 2^51981138 is an apocalyptic number.

51981138 is an abundant number, since it is smaller than the sum of its proper divisors (78119118).

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

51981138 is a wasteful number, since it uses less digits than its factorization.

51981138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15479 (or 15476 counting only the distinct ones).

The product of its digits is 8640, while the sum is 36.

The square root of 51981138 is about 7209.7945879200. The cubic root of 51981138 is about 373.2059803359.

It can be divided in two parts, 5198 and 1138, that added together give a palindrome (6336).

The spelling of 51981138 in words is "fifty-one million, nine hundred eighty-one thousand, one hundred thirty-eight".