81615749 has 2 divisors, whose sum is σ = 81615750. Its totient is φ = 81615748.

The previous prime is 81615733. The next prime is 81615817. The reversal of 81615749 is 94751618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 60730849 + 20884900 = 7793^2 + 4570^2 .

It is a cyclic number.

It is not a de Polignac number, because 81615749 - 2⁴ = 81615733 is a prime.

It is a super-2 number, since 2×81615749² = 13322260969662002, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81615049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40807874 + 40807875.

It is an arithmetic number, because the mean of its divisors is an integer number (40807875).

Almost surely, 2^81615749 is an apocalyptic number.

It is an amenable number.

81615749 is a deficient number, since it is larger than the sum of its proper divisors (1).

81615749 is an equidigital number, since it uses as much as digits as its factorization.

81615749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 41.

The square root of 81615749 is about 9034.1435122539. The cubic root of 81615749 is about 433.7684795865.

The spelling of 81615749 in words is "eighty-one million, six hundred fifteen thousand, seven hundred forty-nine".