81358691 has 4 divisors (see below), whose sum is σ = 81376800. Its totient is φ = 81340584.

The previous prime is 81358681. The next prime is 81358721. The reversal of 81358691 is 19685318.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81358691 - 2¹⁴ = 81342307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81358681) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3350 + ... + 13188.

It is an arithmetic number, because the mean of its divisors is an integer number (20344200).

Almost surely, 2^81358691 is an apocalyptic number.

81358691 is a deficient number, since it is larger than the sum of its proper divisors (18109).

81358691 is an equidigital number, since it uses as much as digits as its factorization.

81358691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18108.

The product of its digits is 51840, while the sum is 41.

The square root of 81358691 is about 9019.9052655779. The cubic root of 81358691 is about 433.3125997312.

The spelling of 81358691 in words is "eighty-one million, three hundred fifty-eight thousand, six hundred ninety-one".