81972913 has 8 divisors (see below), whose sum is σ = 90311616. Its totient is φ = 73782000.

The previous prime is 81972911. The next prime is 81972949. The reversal of 81972913 is 31927918.

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 81972913 - 2¹ = 81972911 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81972911) 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, 35781 + ... + 38002.

It is an arithmetic number, because the mean of its divisors is an integer number (11288952).

Almost surely, 2^81972913 is an apocalyptic number.

It is an amenable number.

81972913 is a deficient number, since it is larger than the sum of its proper divisors (8338703).

81972913 is a wasteful number, since it uses less digits than its factorization.

81972913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73895.

The product of its digits is 27216, while the sum is 40.

The square root of 81972913 is about 9053.8893852311. The cubic root of 81972913 is about 434.4003063289.

The spelling of 81972913 in words is "eighty-one million, nine hundred seventy-two thousand, nine hundred thirteen".