15977981 has 2 divisors, whose sum is σ = 15977982. Its totient is φ = 15977980.

The previous prime is 15977971. The next prime is 15978023. The reversal of 15977981 is 18977951.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15960025 + 17956 = 3995^2 + 134^2 .

It is a cyclic number.

It is not a de Polignac number, because 15977981 - 2¹⁴ = 15961597 is a prime.

It is a super-2 number, since 2×15977981² = 510591753672722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15977921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7988990 + 7988991.

It is an arithmetic number, because the mean of its divisors is an integer number (7988991).

Almost surely, 2^15977981 is an apocalyptic number.

It is an amenable number.

15977981 is a deficient number, since it is larger than the sum of its proper divisors (1).

15977981 is an equidigital number, since it uses as much as digits as its factorization.

15977981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 158760, while the sum is 47.

The square root of 15977981 is about 3997.2466774018. The cubic root of 15977981 is about 251.8685644061.

The spelling of 15977981 in words is "fifteen million, nine hundred seventy-seven thousand, nine hundred eighty-one".