18251621 has 2 divisors, whose sum is σ = 18251622. Its totient is φ = 18251620.

The previous prime is 18251603. The next prime is 18251687. The reversal of 18251621 is 12615281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15100996 + 3150625 = 3886^2 + 1775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18251621 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 (18251021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9125810 + 9125811.

It is an arithmetic number, because the mean of its divisors is an integer number (9125811).

Almost surely, 2^18251621 is an apocalyptic number.

It is an amenable number.

18251621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18251621 is an equidigital number, since it uses as much as digits as its factorization.

18251621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 960, while the sum is 26.

The square root of 18251621 is about 4272.1915921457. The cubic root of 18251621 is about 263.2896662447.

The spelling of 18251621 in words is "eighteen million, two hundred fifty-one thousand, six hundred twenty-one".