81798521 has 4 divisors (see below), whose sum is σ = 93484032. Its totient is φ = 70113012.

The previous prime is 81798517. The next prime is 81798529. The reversal of 81798521 is 12589718.

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 81798521 - 2² = 81798517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81798529) 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, 5842745 + ... + 5842758.

It is an arithmetic number, because the mean of its divisors is an integer number (23371008).

Almost surely, 2^81798521 is an apocalyptic number.

It is an amenable number.

81798521 is a deficient number, since it is larger than the sum of its proper divisors (11685511).

81798521 is a wasteful number, since it uses less digits than its factorization.

81798521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11685510.

The product of its digits is 40320, while the sum is 41.

The square root of 81798521 is about 9044.2534794200. The cubic root of 81798521 is about 434.0920348891.

The spelling of 81798521 in words is "eighty-one million, seven hundred ninety-eight thousand, five hundred twenty-one".