81361639 has 16 divisors (see below), whose sum is σ = 86053120. Its totient is φ = 76826880.

The previous prime is 81361627. The next prime is 81361691. The reversal of 81361639 is 93616318.

It is a cyclic number.

It is not a de Polignac number, because 81361639 - 2⁹ = 81361127 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81361598 and 81361607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81361619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 355177 + ... + 355405.

It is an arithmetic number, because the mean of its divisors is an integer number (5378320).

Almost surely, 2^81361639 is an apocalyptic number.

81361639 is a deficient number, since it is larger than the sum of its proper divisors (4691481).

81361639 is a wasteful number, since it uses less digits than its factorization.

81361639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 490.

The product of its digits is 23328, while the sum is 37.

The square root of 81361639 is about 9020.0686804481. The cubic root of 81361639 is about 433.3178333049.

The spelling of 81361639 in words is "eighty-one million, three hundred sixty-one thousand, six hundred thirty-nine".