51731921 has 4 divisors (see below), whose sum is σ = 51880500. Its totient is φ = 51583344.

The previous prime is 51731917. The next prime is 51731923. The reversal of 51731921 is 12913715.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 47886400 + 3845521 = 6920^2 + 1961^2 .

It is a cyclic number.

It is not a de Polignac number, because 51731921 - 2² = 51731917 is a prime.

It is a super-3 number, since 3×51731921³ (a number of 24 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51731923) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 73766 + ... + 74463.

It is an arithmetic number, because the mean of its divisors is an integer number (12970125).

Almost surely, 2^51731921 is an apocalyptic number.

It is an amenable number.

51731921 is a deficient number, since it is larger than the sum of its proper divisors (148579).

51731921 is a wasteful number, since it uses less digits than its factorization.

51731921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148578.

The product of its digits is 1890, while the sum is 29.

The square root of 51731921 is about 7192.4905978388. The cubic root of 51731921 is about 372.6085949767.

The spelling of 51731921 in words is "fifty-one million, seven hundred thirty-one thousand, nine hundred twenty-one".