21779240 has 32 divisors (see below), whose sum is σ = 56004480. Its totient is φ = 7467072.

The previous prime is 21779239. The next prime is 21779243. The reversal of 21779240 is 4297712.

It is a junction number, because it is equal to n+sod(n) for n = 21779197 and 21779206.

It is not an unprimeable number, because it can be changed into a prime (21779243) 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, 38612 + ... + 39171.

It is an arithmetic number, because the mean of its divisors is an integer number (1750140).

Almost surely, 2^21779240 is an apocalyptic number.

21779240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21779240 is an abundant number, since it is smaller than the sum of its proper divisors (34225240).

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

21779240 is a wasteful number, since it uses less digits than its factorization.

21779240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77801 (or 77797 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21779240 is about 4666.8233307037. The cubic root of 21779240 is about 279.2635408456.

The spelling of 21779240 in words is "twenty-one million, seven hundred seventy-nine thousand, two hundred forty".