51918991 has 4 divisors (see below), whose sum is σ = 52770184. Its totient is φ = 51067800.

The previous prime is 51918967. The next prime is 51919013. The reversal of 51918991 is 19981915.

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

It is a cyclic number.

It is not a de Polignac number, because 51918991 - 2¹⁹ = 51394703 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 (51918491) 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, 425505 + ... + 425626.

It is an arithmetic number, because the mean of its divisors is an integer number (13192546).

Almost surely, 2^51918991 is an apocalyptic number.

51918991 is a deficient number, since it is larger than the sum of its proper divisors (851193).

51918991 is an equidigital number, since it uses as much as digits as its factorization.

51918991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 851192.

The product of its digits is 29160, while the sum is 43.

The square root of 51918991 is about 7205.4833980795. The cubic root of 51918991 is about 373.0571899458.

The spelling of 51918991 in words is "fifty-one million, nine hundred eighteen thousand, nine hundred ninety-one".