51991663 has 2 divisors, whose sum is σ = 51991664. Its totient is φ = 51991662.

The previous prime is 51991651. The next prime is 51991711. The reversal of 51991663 is 36619915.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 51991663 - 2⁵ = 51991631 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51991603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25995831 + 25995832.

It is an arithmetic number, because the mean of its divisors is an integer number (25995832).

Almost surely, 2^51991663 is an apocalyptic number.

51991663 is a deficient number, since it is larger than the sum of its proper divisors (1).

51991663 is an equidigital number, since it uses as much as digits as its factorization.

51991663 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43740, while the sum is 40.

The square root of 51991663 is about 7210.5244608142. The cubic root of 51991663 is about 373.2311672146.

The spelling of 51991663 in words is "fifty-one million, nine hundred ninety-one thousand, six hundred sixty-three".