81664451 has 8 divisors (see below), whose sum is σ = 93777600. Its totient is φ = 70332840.

The previous prime is 81664441. The next prime is 81664463. The reversal of 81664451 is 15446618.

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 81664451 - 2¹⁴ = 81648067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81664441) 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, 195161 + ... + 195578.

It is an arithmetic number, because the mean of its divisors is an integer number (11722200).

Almost surely, 2^81664451 is an apocalyptic number.

81664451 is a deficient number, since it is larger than the sum of its proper divisors (12113149).

81664451 is a wasteful number, since it uses less digits than its factorization.

81664451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390769.

The product of its digits is 23040, while the sum is 35.

The square root of 81664451 is about 9036.8385511749. The cubic root of 81664451 is about 433.8547423162.

The spelling of 81664451 in words is "eighty-one million, six hundred sixty-four thousand, four hundred fifty-one".