18640261 has 2 divisors, whose sum is σ = 18640262. Its totient is φ = 18640260.

The previous prime is 18640253. The next prime is 18640277. The reversal of 18640261 is 16204681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17589636 + 1050625 = 4194^2 + 1025^2 .

It is a cyclic number.

It is not a de Polignac number, because 18640261 - 2³ = 18640253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18640241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9320130 + 9320131.

It is an arithmetic number, because the mean of its divisors is an integer number (9320131).

Almost surely, 2^18640261 is an apocalyptic number.

It is an amenable number.

18640261 is a deficient number, since it is larger than the sum of its proper divisors (1).

18640261 is an equidigital number, since it uses as much as digits as its factorization.

18640261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 18640261 is about 4317.4368553576. The cubic root of 18640261 is about 265.1453385732.

The spelling of 18640261 in words is "eighteen million, six hundred forty thousand, two hundred sixty-one".