21799840 has 96 divisors (see below), whose sum is σ = 55520640. Its totient is φ = 8064000.

The previous prime is 21799829. The next prime is 21799849. The reversal of 21799840 is 4899712.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 21799793 and 21799802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21799849) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 215790 + ... + 215890.

It is an arithmetic number, because the mean of its divisors is an integer number (578340).

Almost surely, 2^21799840 is an apocalyptic number.

21799840 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 21799840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27760320).

21799840 is an abundant number, since it is smaller than the sum of its proper divisors (33720800).

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

21799840 is a wasteful number, since it uses less digits than its factorization.

21799840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 198 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 21799840 is about 4669.0298778226. The cubic root of 21799840 is about 279.3515606925.

The spelling of 21799840 in words is "twenty-one million, seven hundred ninety-nine thousand, eight hundred forty".