157321981 has 2 divisors, whose sum is σ = 157321982. Its totient is φ = 157321980.

The previous prime is 157321973. The next prime is 157321991. The reversal of 157321981 is 189123751.

157321981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 145419481 + 11902500 = 12059^2 + 3450^2 .

It is an emirp because it is prime and its reverse (189123751) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 157321981 - 2³ = 157321973 is a prime.

It is a super-2 number, since 2×157321981² = 49500411411528722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 157321981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (157321921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 78660990 + 78660991.

It is an arithmetic number, because the mean of its divisors is an integer number (78660991).

Almost surely, 2^157321981 is an apocalyptic number.

It is an amenable number.

157321981 is a deficient number, since it is larger than the sum of its proper divisors (1).

157321981 is an equidigital number, since it uses as much as digits as its factorization.

157321981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15120, while the sum is 37.

The square root of 157321981 is about 12542.8059460393. The cubic root of 157321981 is about 539.8376066327.

The spelling of 157321981 in words is "one hundred fifty-seven million, three hundred twenty-one thousand, nine hundred eighty-one".