18491621 has 2 divisors, whose sum is σ = 18491622. Its totient is φ = 18491620.

The previous prime is 18491573. The next prime is 18491639. The reversal of 18491621 is 12619481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18395521 + 96100 = 4289^2 + 310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18491621 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18491651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9245810 + 9245811.

It is an arithmetic number, because the mean of its divisors is an integer number (9245811).

Almost surely, 2^18491621 is an apocalyptic number.

It is an amenable number.

18491621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18491621 is an equidigital number, since it uses as much as digits as its factorization.

18491621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 32.

The square root of 18491621 is about 4300.1884842411. The cubic root of 18491621 is about 264.4386884809.

The spelling of 18491621 in words is "eighteen million, four hundred ninety-one thousand, six hundred twenty-one".