18406621 has 2 divisors, whose sum is σ = 18406622. Its totient is φ = 18406620.

The previous prime is 18406607. The next prime is 18406627. The reversal of 18406621 is 12660481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10169721 + 8236900 = 3189^2 + 2870^2 .

It is a cyclic number.

It is not a de Polignac number, because 18406621 - 2⁹ = 18406109 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18406621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18406627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9203310 + 9203311.

It is an arithmetic number, because the mean of its divisors is an integer number (9203311).

Almost surely, 2^18406621 is an apocalyptic number.

It is an amenable number.

18406621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18406621 is an equidigital number, since it uses as much as digits as its factorization.

18406621 is an evil number, because the sum of its binary digits is even.

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

The square root of 18406621 is about 4290.2938127825. The cubic root of 18406621 is about 264.0328863608.

The spelling of 18406621 in words is "eighteen million, four hundred six thousand, six hundred twenty-one".