21986240 has 56 divisors (see below), whose sum is σ = 52864512. Its totient is φ = 8709120.

The previous prime is 21986233. The next prime is 21986243. The reversal of 21986240 is 4268912.

21986240 = T₁₉₉ + T₂₀₀ + ... + T₅₁₈.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 21986197 and 21986206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21986243) 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, 40370 + ... + 40910.

Almost surely, 2^21986240 is an apocalyptic number.

21986240 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 21986240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26432256).

21986240 is an abundant number, since it is smaller than the sum of its proper divisors (30878272).

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

21986240 is a wasteful number, since it uses less digits than its factorization.

21986240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 685 (or 675 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21986240 is about 4688.9487094657. The cubic root of 21986240 is about 280.1455026074.

The spelling of 21986240 in words is "twenty-one million, nine hundred eighty-six thousand, two hundred forty".