157123721 has 2 divisors, whose sum is σ = 157123722. Its totient is φ = 157123720.

The previous prime is 157123709. The next prime is 157123727. The reversal of 157123721 is 127321751.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 156750400 + 373321 = 12520^2 + 611^2 .

It is a cyclic number.

It is not a de Polignac number, because 157123721 - 2²⁶ = 90014857 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (157123727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 78561860 + 78561861.

It is an arithmetic number, because the mean of its divisors is an integer number (78561861).

Almost surely, 2^157123721 is an apocalyptic number.

It is an amenable number.

157123721 is a deficient number, since it is larger than the sum of its proper divisors (1).

157123721 is an equidigital number, since it uses as much as digits as its factorization.

157123721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2940, while the sum is 29.

The square root of 157123721 is about 12534.9001192670. The cubic root of 157123721 is about 539.6107402738.

The spelling of 157123721 in words is "one hundred fifty-seven million, one hundred twenty-three thousand, seven hundred twenty-one".