51821631 has 24 divisors (see below), whose sum is σ = 76383216. Its totient is φ = 33849600.

The previous prime is 51821629. The next prime is 51821633. The reversal of 51821631 is 13612815.

51821631 is a `hidden beast` number, since 5 + 1 + 8 + 21 + 631 = 666.

It is an interprime number because it is at equal distance from previous prime (51821629) and next prime (51821633).

It is not a de Polignac number, because 51821631 - 2¹ = 51821629 is a prime.

It is a super-2 number, since 2×51821631² = 5370962879000322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 51821595 and 51821604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51821633) 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, 129031 + ... + 129431.

It is an arithmetic number, because the mean of its divisors is an integer number (3182634).

Almost surely, 2^51821631 is an apocalyptic number.

51821631 is a deficient number, since it is larger than the sum of its proper divisors (24561585).

51821631 is a wasteful number, since it uses less digits than its factorization.

51821631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 663 (or 660 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 51821631 is about 7198.7242619786. The cubic root of 51821631 is about 372.8238548065.

The spelling of 51821631 in words is "fifty-one million, eight hundred twenty-one thousand, six hundred thirty-one".