21642180 has 72 divisors (see below), whose sum is σ = 69561408. Its totient is φ = 4924992.

The previous prime is 21642169. The next prime is 21642191. The reversal of 21642180 is 8124612.

It is an interprime number because it is at equal distance from previous prime (21642169) and next prime (21642191).

It is a self number, because there is not a number n which added to its sum of digits gives 21642180.

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, 95227 + ... + 95453.

Almost surely, 2^21642180 is an apocalyptic number.

21642180 is a gapful number since it is divisible by the number (20) 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 21642180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34780704).

21642180 is an abundant number, since it is smaller than the sum of its proper divisors (47919228).

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

21642180 is a wasteful number, since it uses less digits than its factorization.

21642180 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473 (or 244 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21642180 is about 4652.1156477457. The cubic root of 21642180 is about 278.6764919754.

Adding to 21642180 its reverse (8124612), we get a palindrome (29766792).

The spelling of 21642180 in words is "twenty-one million, six hundred forty-two thousand, one hundred eighty".