18491920 has 40 divisors (see below), whose sum is σ = 45526104. Its totient is φ = 6961152.

The previous prime is 18491917. The next prime is 18491927. The reversal of 18491920 is 2919481.

It can be written as a sum of positive squares in 4 ways, for example, as 952576 + 17539344 = 976^2 + 4188^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×18491920² = 683902210572800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18491927) 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, 5439 + ... + 8158.

Almost surely, 2^18491920 is an apocalyptic number.

18491920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

18491920 is the 2720-th heptagonal number.

It is an amenable number.

18491920 is an abundant number, since it is smaller than the sum of its proper divisors (27034184).

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

18491920 is a wasteful number, since it uses less digits than its factorization.

18491920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13627 (or 13621 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 18491920 is about 4300.2232500185. The cubic root of 18491920 is about 264.4401137524.

The spelling of 18491920 in words is "eighteen million, four hundred ninety-one thousand, nine hundred twenty".