18640621 has 2 divisors, whose sum is σ = 18640622. Its totient is φ = 18640620.

The previous prime is 18640561. The next prime is 18640639. The reversal of 18640621 is 12604681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13286025 + 5354596 = 3645^2 + 2314^2 .

It is a cyclic number.

It is not a de Polignac number, because 18640621 - 2¹¹ = 18638573 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18640621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18640681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9320310 + 9320311.

It is an arithmetic number, because the mean of its divisors is an integer number (9320311).

Almost surely, 2^18640621 is an apocalyptic number.

It is an amenable number.

18640621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18640621 is an equidigital number, since it uses as much as digits as its factorization.

18640621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 18640621 is about 4317.4785465593. The cubic root of 18640621 is about 265.1470454825.

The spelling of 18640621 in words is "eighteen million, six hundred forty thousand, six hundred twenty-one".