81691452997 has 16 divisors (see below), whose sum is σ = 101857480704. Its totient is φ = 63650430000.

The previous prime is 81691452989. The next prime is 81691453007. The reversal of 81691452997 is 79925419618.

It is a cyclic number.

It is not a de Polignac number, because 81691452997 - 2³ = 81691452989 is a prime.

It is a super-2 number, since 2×81691452997² (a number of 23 digits) contains 22 as substring.

Its product of digits (9797760) is a multiple of the sum of its prime divisors (87480).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81691452977) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1083972 + ... + 1156882.

It is an arithmetic number, because the mean of its divisors is an integer number (6366092544).

Almost surely, 2^81691452997 is an apocalyptic number.

It is an amenable number.

81691452997 is a deficient number, since it is larger than the sum of its proper divisors (20166027707).

81691452997 is a wasteful number, since it uses less digits than its factorization.

81691452997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87480.

The product of its digits is 9797760, while the sum is 61.

The spelling of 81691452997 in words is "eighty-one billion, six hundred ninety-one million, four hundred fifty-two thousand, nine hundred ninety-seven".