81393451 has 4 divisors (see below), whose sum is σ = 83593312. Its totient is φ = 79193592.

The previous prime is 81393427. The next prime is 81393457. The reversal of 81393451 is 15439318.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81393451 - 2⁵ = 81393419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81393457) 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 3 ways as a sum of consecutive naturals, for example, 1099875 + ... + 1099948.

It is an arithmetic number, because the mean of its divisors is an integer number (20898328).

Almost surely, 2^81393451 is an apocalyptic number.

81393451 is a deficient number, since it is larger than the sum of its proper divisors (2199861).

81393451 is a wasteful number, since it uses less digits than its factorization.

81393451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2199860.

The product of its digits is 12960, while the sum is 34.

The square root of 81393451 is about 9021.8319093186. The cubic root of 81393451 is about 433.3743009920.

The spelling of 81393451 in words is "eighty-one million, three hundred ninety-three thousand, four hundred fifty-one".