18990990 has 64 divisors (see below), whose sum is σ = 52038720. Its totient is φ = 4924800.

The previous prime is 18990973. The next prime is 18990991. The reversal of 18990990 is 9909981.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18990991) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9040 + ... + 10940.

It is an arithmetic number, because the mean of its divisors is an integer number (813105).

Almost surely, 2^18990990 is an apocalyptic number.

18990990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 18990990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26019360).

18990990 is an abundant number, since it is smaller than the sum of its proper divisors (33047730).

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

18990990 is a wasteful number, since it uses less digits than its factorization.

18990990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1954 (or 1948 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 45.

The square root of 18990990 is about 4357.8653031043. The cubic root of 18990990 is about 266.7979787314.

The spelling of 18990990 in words is "eighteen million, nine hundred ninety thousand, nine hundred ninety".