81616637 has 2 divisors, whose sum is σ = 81616638. Its totient is φ = 81616636.

The previous prime is 81616631. The next prime is 81616651. The reversal of 81616637 is 73661618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81613156 + 3481 = 9034^2 + 59^2 .

It is a cyclic number.

It is not a de Polignac number, because 81616637 - 2⁴ = 81616621 is a prime.

It is a super-2 number, since 2×81616637² = 13322550870379538, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81616637.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81616631) 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 as a sum of consecutive naturals, namely, 40808318 + 40808319.

It is an arithmetic number, because the mean of its divisors is an integer number (40808319).

Almost surely, 2^81616637 is an apocalyptic number.

It is an amenable number.

81616637 is a deficient number, since it is larger than the sum of its proper divisors (1).

81616637 is an equidigital number, since it uses as much as digits as its factorization.

81616637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 38.

The square root of 81616637 is about 9034.1926590039. The cubic root of 81616637 is about 433.7700527511.

The spelling of 81616637 in words is "eighty-one million, six hundred sixteen thousand, six hundred thirty-seven".