81615949 has 2 divisors, whose sum is σ = 81615950. Its totient is φ = 81615948.

The previous prime is 81615943. The next prime is 81615959. The reversal of 81615949 is 94951618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 42640900 + 38975049 = 6530^2 + 6243^2 .

It is a cyclic number.

It is not a de Polignac number, because 81615949 - 2¹¹ = 81613901 is a prime.

It is a super-2 number, since 2×81615949² = 13322326262341202, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81615943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40807974 + 40807975.

It is an arithmetic number, because the mean of its divisors is an integer number (40807975).

Almost surely, 2^81615949 is an apocalyptic number.

It is an amenable number.

81615949 is a deficient number, since it is larger than the sum of its proper divisors (1).

81615949 is an equidigital number, since it uses as much as digits as its factorization.

81615949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 77760, while the sum is 43.

The square root of 81615949 is about 9034.1545813651. The cubic root of 81615949 is about 433.7688339039.

The spelling of 81615949 in words is "eighty-one million, six hundred fifteen thousand, nine hundred forty-nine".