51921 has 10 divisors (see below), whose sum is σ = 77682. Its totient is φ = 34560.

The previous prime is 51913. The next prime is 51929. The reversal of 51921 is 12915.

51921 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (51913) and next prime (51929).

It can be written as a sum of positive squares in only one way, i.e., 50625 + 1296 = 225^2 + 36^2 .

It is not a de Polignac number, because 51921 - 2³ = 51913 is a prime.

It is a Curzon number.

51921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 51894 and 51903.

It is not an unprimeable number, because it can be changed into a prime (51929) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 240 + ... + 401.

2⁵¹⁹²¹ is an apocalyptic number.

It is an amenable number.

51921 is a deficient number, since it is larger than the sum of its proper divisors (25761).

51921 is an equidigital number, since it uses as much as digits as its factorization.

51921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 653 (or 644 counting only the distinct ones).

The product of its digits is 90, while the sum is 18.

The square root of 51921 is about 227.8618002211. The cubic root of 51921 is about 37.3062001687.

It can be divided in two parts, 51 and 921, that multiplied together give a triangular number (46971 = T₃₀₆).

The spelling of 51921 in words is "fifty-one thousand, nine hundred twenty-one".