21642120 has 128 divisors (see below), whose sum is σ = 74736000. Its totient is φ = 5564160.

The previous prime is 21642119. The next prime is 21642133. The reversal of 21642120 is 2124612.

21642120 is a `hidden beast` number, since 2 + 1 + 642 + 1 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21642093 and 21642102.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30975 + ... + 31665.

It is an arithmetic number, because the mean of its divisors is an integer number (583875).

Almost surely, 2^21642120 is an apocalyptic number.

21642120 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 21642120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37368000).

21642120 is an abundant number, since it is smaller than the sum of its proper divisors (53093880).

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

21642120 is a wasteful number, since it uses less digits than its factorization.

21642120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 740 (or 730 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21642120 is about 4652.1091990623. The cubic root of 21642120 is about 278.6762344443.

Adding to 21642120 its reverse (2124612), we get a palindrome (23766732).

The spelling of 21642120 in words is "twenty-one million, six hundred forty-two thousand, one hundred twenty".