81790866 has 12 divisors (see below), whose sum is σ = 177213582. Its totient is φ = 27263616.

The previous prime is 81790861. The next prime is 81790867. The reversal of 81790866 is 66809718.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 52142841 + 29648025 = 7221^2 + 5445^2 .

It is a super-2 number, since 2×81790866² = 13379491522059912, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81790861) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2271951 + ... + 2271986.

Almost surely, 2^81790866 is an apocalyptic number.

81790866 is an abundant number, since it is smaller than the sum of its proper divisors (95422716).

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

81790866 is a wasteful number, since it uses less digits than its factorization.

81790866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4543945 (or 4543942 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The square root of 81790866 is about 9043.8302726223. The cubic root of 81790866 is about 434.0784931684.

The spelling of 81790866 in words is "eighty-one million, seven hundred ninety thousand, eight hundred sixty-six".