81247979 has 4 divisors (see below), whose sum is σ = 81466176. Its totient is φ = 81029784.

The previous prime is 81247973. The next prime is 81248039. The reversal of 81247979 is 97974218.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81247979 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81247973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108539 + ... + 109284.

It is an arithmetic number, because the mean of its divisors is an integer number (20366544).

Almost surely, 2^81247979 is an apocalyptic number.

81247979 is a deficient number, since it is larger than the sum of its proper divisors (218197).

81247979 is a wasteful number, since it uses less digits than its factorization.

81247979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218196.

The product of its digits is 254016, while the sum is 47.

The square root of 81247979 is about 9013.7660830532. The cubic root of 81247979 is about 433.1159615243.

The spelling of 81247979 in words is "eighty-one million, two hundred forty-seven thousand, nine hundred seventy-nine".