81978523 has 8 divisors (see below), whose sum is σ = 90437040. Its totient is φ = 73687680.

The previous prime is 81978499. The next prime is 81978527. The reversal of 81978523 is 32587918.

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

It is not a de Polignac number, because 81978523 - 2²⁵ = 48424091 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81978523.

It is not an unprimeable number, because it can be changed into a prime (81978527) 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, 40890 + ... + 42847.

It is an arithmetic number, because the mean of its divisors is an integer number (11304630).

Almost surely, 2^81978523 is an apocalyptic number.

81978523 is a deficient number, since it is larger than the sum of its proper divisors (8458517).

81978523 is a wasteful number, since it uses less digits than its factorization.

81978523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83837.

The product of its digits is 120960, while the sum is 43.

The square root of 81978523 is about 9054.1991915354. The cubic root of 81978523 is about 434.4102158223.

The spelling of 81978523 in words is "eighty-one million, nine hundred seventy-eight thousand, five hundred twenty-three".