21778240 has 112 divisors (see below), whose sum is σ = 59253120. Its totient is φ = 7546880.

The previous prime is 21778223. The next prime is 21778259. The reversal of 21778240 is 4287712.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

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, 80826 + ... + 81094.

Almost surely, 2^21778240 is an apocalyptic number.

21778240 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 21778240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29626560).

21778240 is an abundant number, since it is smaller than the sum of its proper divisors (37474880).

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

21778240 is a wasteful number, since it uses less digits than its factorization.

21778240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320 (or 310 counting only the distinct ones).

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 21778240 is about 4666.7161902134. The cubic root of 21778240 is about 279.2592666252.

The spelling of 21778240 in words is "twenty-one million, seven hundred seventy-eight thousand, two hundred forty".