81321668 has 12 divisors (see below), whose sum is σ = 142383612. Its totient is φ = 40640640.

The previous prime is 81321641. The next prime is 81321673. The reversal of 81321668 is 86612318.

It can be written as a sum of positive squares in 2 ways, for example, as 3564544 + 77757124 = 1888^2 + 8818^2 .

It is a super-2 number, since 2×81321668² = 13226427372604448, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7448 + ... + 14768.

It is an arithmetic number, because the mean of its divisors is an integer number (11865301).

Almost surely, 2^81321668 is an apocalyptic number.

It is an amenable number.

81321668 is a deficient number, since it is larger than the sum of its proper divisors (61061944).

81321668 is a wasteful number, since it uses less digits than its factorization.

81321668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10102 (or 10100 counting only the distinct ones).

The product of its digits is 13824, while the sum is 35.

The square root of 81321668 is about 9017.8527377641. The cubic root of 81321668 is about 433.2468621674.

The spelling of 81321668 in words is "eighty-one million, three hundred twenty-one thousand, six hundred sixty-eight".