18481621 has 2 divisors, whose sum is σ = 18481622. Its totient is φ = 18481620.

The previous prime is 18481583. The next prime is 18481637. The reversal of 18481621 is 12618481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 34596 = 4295^2 + 186^2 .

It is an emirp because it is prime and its reverse (12618481) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18481621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18481321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9240810 + 9240811.

It is an arithmetic number, because the mean of its divisors is an integer number (9240811).

Almost surely, 2^18481621 is an apocalyptic number.

It is an amenable number.

18481621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18481621 is an equidigital number, since it uses as much as digits as its factorization.

18481621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3072, while the sum is 31.

The square root of 18481621 is about 4299.0255872697. The cubic root of 18481621 is about 264.3910116852.

The spelling of 18481621 in words is "eighteen million, four hundred eighty-one thousand, six hundred twenty-one".