21898440 has 96 divisors (see below), whose sum is σ = 72446400. Its totient is φ = 5735040.

The previous prime is 21898433. The next prime is 21898441. The reversal of 21898440 is 4489812.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21898395 and 21898404.

It is not an unprimeable number, because it can be changed into a prime (21898441) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20725 + ... + 21755.

It is an arithmetic number, because the mean of its divisors is an integer number (754650).

Almost surely, 2^21898440 is an apocalyptic number.

21898440 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 21898440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36223200).

21898440 is an abundant number, since it is smaller than the sum of its proper divisors (50547960).

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

21898440 is a wasteful number, since it uses less digits than its factorization.

21898440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1107 (or 1100 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 21898440 is about 4679.5769039519. The cubic root of 21898440 is about 279.7720934569.

It can be divided in two parts, 218984 and 40, that added together give a square (219024 = 468²).

The spelling of 21898440 in words is "twenty-one million, eight hundred ninety-eight thousand, four hundred forty".