18909972 has 72 divisors (see below), whose sum is σ = 50450400. Its totient is φ = 5963328.

The previous prime is 18909949. The next prime is 18909983. The reversal of 18909972 is 27990981.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 61443 + ... + 61749.

It is an arithmetic number, because the mean of its divisors is an integer number (700700).

Almost surely, 2^18909972 is an apocalyptic number.

18909972 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18909972, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25225200).

18909972 is an abundant number, since it is smaller than the sum of its proper divisors (31540428).

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

18909972 is a wasteful number, since it uses less digits than its factorization.

18909972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 405 (or 400 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 18909972 is about 4348.5597615762. The cubic root of 18909972 is about 266.4180397924.

It can be divided in two parts, 18909 and 972, that added together give a square (19881 = 141²).

The spelling of 18909972 in words is "eighteen million, nine hundred nine thousand, nine hundred seventy-two".