18355921 has 2 divisors, whose sum is σ = 18355922. Its totient is φ = 18355920.

The previous prime is 18355891. The next prime is 18355933. The reversal of 18355921 is 12955381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9235521 + 9120400 = 3039^2 + 3020^2 .

It is a cyclic number.

It is not a de Polignac number, because 18355921 - 2⁵ = 18355889 is a prime.

It is not a weakly prime, because it can be changed into another prime (18355021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9177960 + 9177961.

It is an arithmetic number, because the mean of its divisors is an integer number (9177961).

Almost surely, 2^18355921 is an apocalyptic number.

It is an amenable number.

18355921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18355921 is an equidigital number, since it uses as much as digits as its factorization.

18355921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 34.

The square root of 18355921 is about 4284.3810521474. The cubic root of 18355921 is about 263.7902422069.

The spelling of 18355921 in words is "eighteen million, three hundred fifty-five thousand, nine hundred twenty-one".