157431721 has 4 divisors (see below), whose sum is σ = 157466512. Its totient is φ = 157396932.

The previous prime is 157431719. The next prime is 157431731. The reversal of 157431721 is 127134751.

157431721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 157431721 - 2¹ = 157431719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (157431731) 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, 9375 + ... + 20068.

It is an arithmetic number, because the mean of its divisors is an integer number (39366628).

Almost surely, 2^157431721 is an apocalyptic number.

It is an amenable number.

157431721 is a deficient number, since it is larger than the sum of its proper divisors (34791).

157431721 is an equidigital number, since it uses as much as digits as its factorization.

157431721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34790.

The product of its digits is 5880, while the sum is 31.

The square root of 157431721 is about 12547.1798026489. The cubic root of 157431721 is about 539.9630987587.

The spelling of 157431721 in words is "one hundred fifty-seven million, four hundred thirty-one thousand, seven hundred twenty-one".