80721815 has 4 divisors (see below), whose sum is σ = 96866184. Its totient is φ = 64577448.

The previous prime is 80721811. The next prime is 80721829. The reversal of 80721815 is 51812708.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 80721815 - 2² = 80721811 is a prime.

It is a super-2 number, since 2×80721815² = 13032022833788450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (80721811) 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, 8072177 + ... + 8072186.

It is an arithmetic number, because the mean of its divisors is an integer number (24216546).

Almost surely, 2^80721815 is an apocalyptic number.

80721815 is a deficient number, since it is larger than the sum of its proper divisors (16144369).

80721815 is a wasteful number, since it uses less digits than its factorization.

80721815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16144368.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 80721815 is about 8984.5319855850. The cubic root of 80721815 is about 432.1789792645.

It can be divided in two parts, 807 and 21815, that added together give a palindrome (22622).

The spelling of 80721815 in words is "eighty million, seven hundred twenty-one thousand, eight hundred fifteen".