18739561 has 2 divisors, whose sum is σ = 18739562. Its totient is φ = 18739560.

The previous prime is 18739547. The next prime is 18739601. The reversal of 18739561 is 16593781.

It is an a-pointer prime, because the next prime (18739601) can be obtained adding 18739561 to its sum of digits (40).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16933225 + 1806336 = 4115^2 + 1344^2 .

It is a cyclic number.

It is not a de Polignac number, because 18739561 - 2⁷ = 18739433 is a prime.

It is a super-2 number, since 2×18739561² = 702342292945442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18739541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9369780 + 9369781.

It is an arithmetic number, because the mean of its divisors is an integer number (9369781).

Almost surely, 2^18739561 is an apocalyptic number.

It is an amenable number.

18739561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18739561 is an equidigital number, since it uses as much as digits as its factorization.

18739561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 40.

The square root of 18739561 is about 4328.9214592090. The cubic root of 18739561 is about 265.6153305084.

The spelling of 18739561 in words is "eighteen million, seven hundred thirty-nine thousand, five hundred sixty-one".