81628079 has 4 divisors (see below), whose sum is σ = 87907176. Its totient is φ = 75348984.

The previous prime is 81628051. The next prime is 81628103. The reversal of 81628079 is 97082618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97082618 = 2 ⋅48541309.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81628079 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81628039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3139529 + ... + 3139554.

It is an arithmetic number, because the mean of its divisors is an integer number (21976794).

Almost surely, 2^81628079 is an apocalyptic number.

81628079 is a deficient number, since it is larger than the sum of its proper divisors (6279097).

81628079 is a wasteful number, since it uses less digits than its factorization.

81628079 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6279096.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 81628079 is about 9034.8258976031. The cubic root of 81628079 is about 433.7903221684.

The spelling of 81628079 in words is "eighty-one million, six hundred twenty-eight thousand, seventy-nine".