18661820 has 24 divisors (see below), whose sum is σ = 40025664. Its totient is φ = 7305536.

The previous prime is 18661807. The next prime is 18661823. The reversal of 18661820 is 2816681.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18661823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8987 + ... + 10866.

It is an arithmetic number, because the mean of its divisors is an integer number (1667736).

Almost surely, 2^18661820 is an apocalyptic number.

18661820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18661820 is an abundant number, since it is smaller than the sum of its proper divisors (21363844).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18661820 is a wasteful number, since it uses less digits than its factorization.

18661820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19909 (or 19907 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 18661820 is about 4319.9328698488. The cubic root of 18661820 is about 265.2475200106.

The spelling of 18661820 in words is "eighteen million, six hundred sixty-one thousand, eight hundred twenty".