18991620 has 36 divisors (see below), whose sum is σ = 57608460. Its totient is φ = 5064384.

The previous prime is 18991589. The next prime is 18991627. The reversal of 18991620 is 2619981.

It can be written as a sum of positive squares in 2 ways, for example, as 9847044 + 9144576 = 3138^2 + 3024^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (18991627) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 52575 + ... + 52934.

It is an arithmetic number, because the mean of its divisors is an integer number (1600235).

Almost surely, 2^18991620 is an apocalyptic number.

18991620 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18991620 is an abundant number, since it is smaller than the sum of its proper divisors (38616840).

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

18991620 is a wasteful number, since it uses less digits than its factorization.

18991620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105524 (or 105519 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 18991620 is about 4357.9375856017. The cubic root of 18991620 is about 266.8009289176.

It can be divided in two parts, 189 and 91620, that added together give a square (91809 = 303²).

The spelling of 18991620 in words is "eighteen million, nine hundred ninety-one thousand, six hundred twenty".