51881621 has 4 divisors (see below), whose sum is σ = 56598144. Its totient is φ = 47165100.

The previous prime is 51881597. The next prime is 51881623. The reversal of 51881621 is 12618815.

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 a de Polignac number, because none of the positive numbers 2^k-51881621 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51881623) 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, 2358245 + ... + 2358266.

It is an arithmetic number, because the mean of its divisors is an integer number (14149536).

Almost surely, 2^51881621 is an apocalyptic number.

It is an amenable number.

51881621 is a deficient number, since it is larger than the sum of its proper divisors (4716523).

51881621 is a wasteful number, since it uses less digits than its factorization.

51881621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4716522.

The product of its digits is 3840, while the sum is 32.

The square root of 51881621 is about 7202.8897673087. The cubic root of 51881621 is about 372.9676626965.

The spelling of 51881621 in words is "fifty-one million, eight hundred eighty-one thousand, six hundred twenty-one".