18500921 has 2 divisors, whose sum is σ = 18500922. Its totient is φ = 18500920.

The previous prime is 18500887. The next prime is 18500929. The reversal of 18500921 is 12900581.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18181696 + 319225 = 4264^2 + 565^2 .

It is an emirp because it is prime and its reverse (12900581) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18500921 is a prime.

It is not a weakly prime, because it can be changed into another prime (18500929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9250460 + 9250461.

It is an arithmetic number, because the mean of its divisors is an integer number (9250461).

Almost surely, 2^18500921 is an apocalyptic number.

It is an amenable number.

18500921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18500921 is an equidigital number, since it uses as much as digits as its factorization.

18500921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 18500921 is about 4301.2696962641. The cubic root of 18500921 is about 264.4830124774.

The spelling of 18500921 in words is "eighteen million, five hundred thousand, nine hundred twenty-one".