18505861 has 6 divisors (see below), whose sum is σ = 20341286. Its totient is φ = 16823400.

The previous prime is 18505849. The next prime is 18505871. The reversal of 18505861 is 16850581.

It can be written as a sum of positive squares in only one way, i.e., 18404100 + 101761 = 4290^2 + 319^2 .

It is not a de Polignac number, because 18505861 - 2¹⁵ = 18473093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18505811) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 76350 + ... + 76591.

Almost surely, 2^18505861 is an apocalyptic number.

18505861 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18505861 is a deficient number, since it is larger than the sum of its proper divisors (1835425).

18505861 is a wasteful number, since it uses less digits than its factorization.

18505861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152963 (or 152952 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 34.

The square root of 18505861 is about 4301.8439069776. The cubic root of 18505861 is about 264.5065505815.

The spelling of 18505861 in words is "eighteen million, five hundred five thousand, eight hundred sixty-one".