81397989 has 24 divisors (see below), whose sum is σ = 129909312. Its totient is φ = 48850560.

The previous prime is 81397963. The next prime is 81398027. The reversal of 81397989 is 98979318.

It is not a de Polignac number, because 81397989 - 2⁸ = 81397733 is a prime.

It is a super-2 number, since 2×81397989² = 13251265226488242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81390989) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8047 + ... + 15084.

It is an arithmetic number, because the mean of its divisors is an integer number (5412888).

Almost surely, 2^81397989 is an apocalyptic number.

It is an amenable number.

81397989 is a deficient number, since it is larger than the sum of its proper divisors (48511323).

81397989 is a wasteful number, since it uses less digits than its factorization.

81397989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23177 (or 23174 counting only the distinct ones).

The product of its digits is 979776, while the sum is 54.

The square root of 81397989 is about 9022.0834068412. The cubic root of 81397989 is about 433.3823549407.

The spelling of 81397989 in words is "eighty-one million, three hundred ninety-seven thousand, nine hundred eighty-nine".