81625613 has 2 divisors, whose sum is σ = 81625614. Its totient is φ = 81625612.

The previous prime is 81625601. The next prime is 81625637. The reversal of 81625613 is 31652618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63075364 + 18550249 = 7942^2 + 4307^2 .

It is a cyclic number.

It is not a de Polignac number, because 81625613 - 2¹² = 81621517 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81625613.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81625693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40812806 + 40812807.

It is an arithmetic number, because the mean of its divisors is an integer number (40812807).

Almost surely, 2^81625613 is an apocalyptic number.

It is an amenable number.

81625613 is a deficient number, since it is larger than the sum of its proper divisors (1).

81625613 is an equidigital number, since it uses as much as digits as its factorization.

81625613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 32.

The square root of 81625613 is about 9034.6894246565. The cubic root of 81625613 is about 433.7859538280.

The spelling of 81625613 in words is "eighty-one million, six hundred twenty-five thousand, six hundred thirteen".