51816991 has 2 divisors, whose sum is σ = 51816992. Its totient is φ = 51816990.

The previous prime is 51816977. The next prime is 51817001. The reversal of 51816991 is 19961815.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 51816991 - 2⁵ = 51816959 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51816911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25908495 + 25908496.

It is an arithmetic number, because the mean of its divisors is an integer number (25908496).

Almost surely, 2^51816991 is an apocalyptic number.

51816991 is a deficient number, since it is larger than the sum of its proper divisors (1).

51816991 is an equidigital number, since it uses as much as digits as its factorization.

51816991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19440, while the sum is 40.

The square root of 51816991 is about 7198.4019754387. The cubic root of 51816991 is about 372.8127271860.

The spelling of 51816991 in words is "fifty-one million, eight hundred sixteen thousand, nine hundred ninety-one".