81199979 has 8 divisors (see below), whose sum is σ = 93918720. Its totient is φ = 68760936.

The previous prime is 81199933. The next prime is 81199981. The reversal of 81199979 is 97999118.

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 81199979 - 2¹² = 81195883 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81199979.

It is not an unprimeable number, because it can be changed into a prime (81199919) 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, 69299 + ... + 70460.

It is an arithmetic number, because the mean of its divisors is an integer number (11739840).

Almost surely, 2^81199979 is an apocalyptic number.

81199979 is a deficient number, since it is larger than the sum of its proper divisors (12718741).

81199979 is a wasteful number, since it uses less digits than its factorization.

81199979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139849.

The product of its digits is 367416, while the sum is 53.

The square root of 81199979 is about 9011.1030956260. The cubic root of 81199979 is about 433.0306520729.

The spelling of 81199979 in words is "eighty-one million, one hundred ninety-nine thousand, nine hundred seventy-nine".