157121981 has 4 divisors (see below), whose sum is σ = 162190464. Its totient is φ = 152053500.

The previous prime is 157121977. The next prime is 157121983. The reversal of 157121981 is 189121751.

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 157121981 - 2² = 157121977 is a prime.

It is a super-2 number, since 2×157121981² = 49374633826728722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (157121983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2534195 + ... + 2534256.

It is an arithmetic number, because the mean of its divisors is an integer number (40547616).

Almost surely, 2^157121981 is an apocalyptic number.

It is an amenable number.

157121981 is a deficient number, since it is larger than the sum of its proper divisors (5068483).

157121981 is an equidigital number, since it uses as much as digits as its factorization.

157121981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5068482.

The product of its digits is 5040, while the sum is 35.

The square root of 157121981 is about 12534.8307128577. The cubic root of 157121981 is about 539.6087483697.

The spelling of 157121981 in words is "one hundred fifty-seven million, one hundred twenty-one thousand, nine hundred eighty-one".