81913649 has 8 divisors (see below), whose sum is σ = 85709760. Its totient is φ = 78137136.

The previous prime is 81913627. The next prime is 81913669. The reversal of 81913649 is 94631918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81913649 - 2⁸ = 81913393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81913619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4019 + ... + 13415.

It is an arithmetic number, because the mean of its divisors is an integer number (10713720).

Almost surely, 2^81913649 is an apocalyptic number.

It is an amenable number.

81913649 is a deficient number, since it is larger than the sum of its proper divisors (3796111).

81913649 is a wasteful number, since it uses less digits than its factorization.

81913649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9799.

The product of its digits is 46656, while the sum is 41.

The square root of 81913649 is about 9050.6159458901. The cubic root of 81913649 is about 434.2955948845.

The spelling of 81913649 in words is "eighty-one million, nine hundred thirteen thousand, six hundred forty-nine".