21939280 has 80 divisors (see below), whose sum is σ = 56407104. Its totient is φ = 7869440.

The previous prime is 21939277. The next prime is 21939361. The reversal of 21939280 is 8293912.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 94044 + ... + 94276.

Almost surely, 2^21939280 is an apocalyptic number.

21939280 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 21939280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28203552).

21939280 is an abundant number, since it is smaller than the sum of its proper divisors (34467824).

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

21939280 is a wasteful number, since it uses less digits than its factorization.

21939280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364 (or 358 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 21939280 is about 4683.9385136870. The cubic root of 21939280 is about 279.9459079182.

The spelling of 21939280 in words is "twenty-one million, nine hundred thirty-nine thousand, two hundred eighty".