309616981 has 4 divisors (see below), whose sum is σ = 310460992. Its totient is φ = 308772972.

The previous prime is 309616939. The next prime is 309616997. The reversal of 309616981 is 189616903.

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 309616981 - 2²¹ = 307519829 is a prime.

It is a super-2 number, since 2×309616981² = 191725349847108722, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (309616081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 421455 + ... + 422188.

It is an arithmetic number, because the mean of its divisors is an integer number (77615248).

Almost surely, 2^309616981 is an apocalyptic number.

It is an amenable number.

309616981 is a deficient number, since it is larger than the sum of its proper divisors (844011).

309616981 is an equidigital number, since it uses as much as digits as its factorization.

309616981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844010.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 309616981 is about 17595.9364911334. The cubic root of 309616981 is about 676.5110954880.

The spelling of 309616981 in words is "three hundred nine million, six hundred sixteen thousand, nine hundred eighty-one".