5157991721 has 2 divisors, whose sum is σ = 5157991722. Its totient is φ = 5157991720.

The previous prime is 5157991691. The next prime is 5157991759. The reversal of 5157991721 is 1271997515.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2721187225 + 2436804496 = 52165^2 + 49364^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-5157991721 is a prime.

It is not a weakly prime, because it can be changed into another prime (5157991621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2578995860 + 2578995861.

It is an arithmetic number, because the mean of its divisors is an integer number (2578995861).

Almost surely, 2^5157991721 is an apocalyptic number.

It is an amenable number.

5157991721 is a deficient number, since it is larger than the sum of its proper divisors (1).

5157991721 is an equidigital number, since it uses as much as digits as its factorization.

5157991721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 198450, while the sum is 47.

The square root of 5157991721 is about 71819.1598461023. The cubic root of 5157991721 is about 1727.8003072895.

The spelling of 5157991721 in words is "five billion, one hundred fifty-seven million, nine hundred ninety-one thousand, seven hundred twenty-one".