81632689 has 2 divisors, whose sum is σ = 81632690. Its totient is φ = 81632688.

The previous prime is 81632687. The next prime is 81632699. The reversal of 81632689 is 98623618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74097664 + 7535025 = 8608^2 + 2745^2 .

It is a cyclic number.

It is not a de Polignac number, because 81632689 - 2¹ = 81632687 is a prime.

Together with 81632687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81632687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40816344 + 40816345.

It is an arithmetic number, because the mean of its divisors is an integer number (40816345).

Almost surely, 2^81632689 is an apocalyptic number.

It is an amenable number.

81632689 is a deficient number, since it is larger than the sum of its proper divisors (1).

81632689 is an equidigital number, since it uses as much as digits as its factorization.

81632689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 43.

The square root of 81632689 is about 9035.0810178991. The cubic root of 81632689 is about 433.7984882136.

The spelling of 81632689 in words is "eighty-one million, six hundred thirty-two thousand, six hundred eighty-nine".