81745279 has 24 divisors (see below), whose sum is σ = 106178688. Its totient is φ = 62198640.

The previous prime is 81745249. The next prime is 81745291. The reversal of 81745279 is 97254718.

It is a de Polignac number, because none of the positive numbers 2^k-81745279 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81745249) 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 23 ways as a sum of consecutive naturals, for example, 21414 + ... + 24940.

It is an arithmetic number, because the mean of its divisors is an integer number (4424112).

Almost surely, 2^81745279 is an apocalyptic number.

81745279 is a deficient number, since it is larger than the sum of its proper divisors (24433409).

81745279 is a wasteful number, since it uses less digits than its factorization.

81745279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3595 (or 3588 counting only the distinct ones).

The product of its digits is 141120, while the sum is 43.

The square root of 81745279 is about 9041.3095843467. The cubic root of 81745279 is about 433.9978321085.

The spelling of 81745279 in words is "eighty-one million, seven hundred forty-five thousand, two hundred seventy-nine".