81171921 has 8 divisors (see below), whose sum is σ = 108288544. Its totient is φ = 54084960.

The previous prime is 81171869. The next prime is 81171929. The reversal of 81171921 is 12917118.

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

It is not a de Polignac number, because 81171921 - 2⁷ = 81171793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81171929) 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, 45 + ... + 12741.

It is an arithmetic number, because the mean of its divisors is an integer number (13536068).

Almost surely, 2^81171921 is an apocalyptic number.

It is an amenable number.

81171921 is a deficient number, since it is larger than the sum of its proper divisors (27116623).

81171921 is a wasteful number, since it uses less digits than its factorization.

81171921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14831.

The product of its digits is 1008, while the sum is 30.

The square root of 81171921 is about 9009.5461039944. The cubic root of 81171921 is about 432.9807695734.

The spelling of 81171921 in words is "eighty-one million, one hundred seventy-one thousand, nine hundred twenty-one".