18828721 has 2 divisors, whose sum is σ = 18828722. Its totient is φ = 18828720.

The previous prime is 18828713. The next prime is 18828737. The reversal of 18828721 is 12782881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11189025 + 7639696 = 3345^2 + 2764^2 .

It is a cyclic number.

It is not a de Polignac number, because 18828721 - 2³ = 18828713 is a prime.

It is not a weakly prime, because it can be changed into another prime (18828701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9414360 + 9414361.

It is an arithmetic number, because the mean of its divisors is an integer number (9414361).

Almost surely, 2^18828721 is an apocalyptic number.

It is an amenable number.

18828721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18828721 is an equidigital number, since it uses as much as digits as its factorization.

18828721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14336, while the sum is 37.

The square root of 18828721 is about 4339.2074161072. The cubic root of 18828721 is about 266.0359167210.

The spelling of 18828721 in words is "eighteen million, eight hundred twenty-eight thousand, seven hundred twenty-one".