51621 has 4 divisors (see below), whose sum is σ = 68832. Its totient is φ = 34412.

The previous prime is 51613. The next prime is 51631. The reversal of 51621 is 12615.

51621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 51621 - 2³ = 51613 is a prime.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 51621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51631) 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, 8601 + ... + 8606.

It is an arithmetic number, because the mean of its divisors is an integer number (17208).

2⁵¹⁶²¹ is an apocalyptic number.

It is an amenable number.

51621 is a deficient number, since it is larger than the sum of its proper divisors (17211).

51621 is a wasteful number, since it uses less digits than its factorization.

51621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17210.

The product of its digits is 60, while the sum is 15.

The square root of 51621 is about 227.2025528026. The cubic root of 51621 is about 37.2342094837.

Adding to 51621 its product of digits (60), we get a triangular number (51681 = T₃₂₁).

The spelling of 51621 in words is "fifty-one thousand, six hundred twenty-one".