51328991 has 4 divisors (see below), whose sum is σ = 58661712. Its totient is φ = 43996272.

The previous prime is 51328973. The next prime is 51328993. The reversal of 51328991 is 19982315.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51328991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51328993) 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, 3666350 + ... + 3666363.

It is an arithmetic number, because the mean of its divisors is an integer number (14665428).

Almost surely, 2^51328991 is an apocalyptic number.

51328991 is a deficient number, since it is larger than the sum of its proper divisors (7332721).

51328991 is an equidigital number, since it uses as much as digits as its factorization.

51328991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7332720.

The product of its digits is 19440, while the sum is 38.

The square root of 51328991 is about 7164.4253782142. The cubic root of 51328991 is about 371.6386801729.

The spelling of 51328991 in words is "fifty-one million, three hundred twenty-eight thousand, nine hundred ninety-one".