80921821 has 4 divisors (see below), whose sum is σ = 80972892. Its totient is φ = 80870752.

The previous prime is 80921809. The next prime is 80921851. The reversal of 80921821 is 12812908.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 23328900 + 57592921 = 4830^2 + 7589^2 .

It is a cyclic number.

It is not a de Polignac number, because 80921821 - 2⁷ = 80921693 is a prime.

It is a super-2 number, since 2×80921821² = 13096682227912082, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (80921851) 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, 23080 + ... + 26353.

It is an arithmetic number, because the mean of its divisors is an integer number (20243223).

Almost surely, 2^80921821 is an apocalyptic number.

It is an amenable number.

80921821 is a deficient number, since it is larger than the sum of its proper divisors (51071).

80921821 is a wasteful number, since it uses less digits than its factorization.

80921821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51070.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 80921821 is about 8995.6556737127. The cubic root of 80921821 is about 432.5356242722.

The spelling of 80921821 in words is "eighty million, nine hundred twenty-one thousand, eight hundred twenty-one".