81997110721 has 8 divisors (see below), whose sum is σ = 82497018240. Its totient is φ = 81497309568.

The previous prime is 81997110703. The next prime is 81997110731. The reversal of 81997110721 is 12701179918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81997110721 - 2⁷ = 81997110593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81997110731) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1976625 + ... + 2017681.

It is an arithmetic number, because the mean of its divisors is an integer number (10312127280).

Almost surely, 2^81997110721 is an apocalyptic number.

It is an amenable number.

81997110721 is a deficient number, since it is larger than the sum of its proper divisors (499907519).

81997110721 is a wasteful number, since it uses less digits than its factorization.

81997110721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53183.

The product of its (nonzero) digits is 63504, while the sum is 46.

The spelling of 81997110721 in words is "eighty-one billion, nine hundred ninety-seven million, one hundred ten thousand, seven hundred twenty-one".