81164641 has 4 divisors (see below), whose sum is σ = 81528832. Its totient is φ = 80800452.

The previous prime is 81164617. The next prime is 81164651. The reversal of 81164641 is 14646118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81164641 - 2⁹ = 81164129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81164651) 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, 181761 + ... + 182206.

It is an arithmetic number, because the mean of its divisors is an integer number (20382208).

Almost surely, 2^81164641 is an apocalyptic number.

It is an amenable number.

81164641 is a deficient number, since it is larger than the sum of its proper divisors (364191).

81164641 is a wasteful number, since it uses less digits than its factorization.

81164641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364190.

The product of its digits is 4608, while the sum is 31.

The square root of 81164641 is about 9009.1420790217. The cubic root of 81164641 is about 432.9678250551.

The spelling of 81164641 in words is "eighty-one million, one hundred sixty-four thousand, six hundred forty-one".