51861381 has 16 divisors (see below), whose sum is σ = 81238080. Its totient is φ = 29013120.

The previous prime is 51861377. The next prime is 51861391. The reversal of 51861381 is 18316815.

It is not a de Polignac number, because 51861381 - 2² = 51861377 is a prime.

It is a super-2 number, since 2×51861381² = 5379205678454322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51861331) 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, 60016 + ... + 60873.

It is an arithmetic number, because the mean of its divisors is an integer number (5077380).

Almost surely, 2^51861381 is an apocalyptic number.

It is an amenable number.

51861381 is a deficient number, since it is larger than the sum of its proper divisors (29376699).

51861381 is a wasteful number, since it uses less digits than its factorization.

51861381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120916.

The product of its digits is 5760, while the sum is 33.

The square root of 51861381 is about 7201.4846386006. The cubic root of 51861381 is about 372.9191558122.

The spelling of 51861381 in words is "fifty-one million, eight hundred sixty-one thousand, three hundred eighty-one".