81997278 has 32 divisors (see below), whose sum is σ = 179366400. Its totient is φ = 24783360.

The previous prime is 81997271. The next prime is 81997309. The reversal of 81997278 is 87279918.

It is a self number, because there is not a number n which added to its sum of digits gives 81997278.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81997271) 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, 28251 + ... + 31017.

It is an arithmetic number, because the mean of its divisors is an integer number (5605200).

Almost surely, 2^81997278 is an apocalyptic number.

81997278 is an abundant number, since it is smaller than the sum of its proper divisors (97369122).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81997278 is a wasteful number, since it uses less digits than its factorization.

81997278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3232.

The product of its digits is 508032, while the sum is 51.

The square root of 81997278 is about 9055.2348395831. The cubic root of 81997278 is about 434.4433413372.

The spelling of 81997278 in words is "eighty-one million, nine hundred ninety-seven thousand, two hundred seventy-eight".