21890440 has 128 divisors (see below), whose sum is σ = 59875200. Its totient is φ = 7096320.

The previous prime is 21890423. The next prime is 21890461. The reversal of 21890440 is 4409812.

It is a junction number, because it is equal to n+sod(n) for n = 21890399 and 21890408.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 245916 + ... + 246004.

It is an arithmetic number, because the mean of its divisors is an integer number (467775).

Almost surely, 2^21890440 is an apocalyptic number.

21890440 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 21890440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29937600).

21890440 is an abundant number, since it is smaller than the sum of its proper divisors (37984760).

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

21890440 is a wasteful number, since it uses less digits than its factorization.

21890440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167 (or 163 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 21890440 is about 4678.7220477391. The cubic root of 21890440 is about 279.7380202633.

The spelling of 21890440 in words is "twenty-one million, eight hundred ninety thousand, four hundred forty".