21642880 has 64 divisors (see below), whose sum is σ = 59143680. Its totient is φ = 7418880.

The previous prime is 21642871. The next prime is 21642883. The reversal of 21642880 is 8824612.

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (21642883) 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, 2065 + ... + 6895.

It is an arithmetic number, because the mean of its divisors is an integer number (924120).

Almost surely, 2^21642880 is an apocalyptic number.

21642880 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 21642880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29571840).

21642880 is an abundant number, since it is smaller than the sum of its proper divisors (37500800).

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

21642880 is an equidigital number, since it uses as much as digits as its factorization.

21642880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4857 (or 4845 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 31.

The square root of 21642880 is about 4652.1908817244. The cubic root of 21642880 is about 278.6794964701.

It can be divided in two parts, 21642 and 880, that added together give a palindrome (22522).

The spelling of 21642880 in words is "twenty-one million, six hundred forty-two thousand, eight hundred eighty".