21987040 has 48 divisors (see below), whose sum is σ = 52390800. Its totient is φ = 8719360.

The previous prime is 21987019. The next prime is 21987041. The reversal of 21987040 is 4078912.

It is a junction number, because it is equal to n+sod(n) for n = 21986993 and 21987011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987041) 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, 20436 + ... + 21484.

It is an arithmetic number, because the mean of its divisors is an integer number (1091475).

Almost surely, 2^21987040 is an apocalyptic number.

21987040 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 21987040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26195400).

21987040 is an abundant number, since it is smaller than the sum of its proper divisors (30403760).

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

21987040 is a wasteful number, since it uses less digits than its factorization.

21987040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1195 (or 1187 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21987040 is about 4689.0340156582. The cubic root of 21987040 is about 280.1489003945.

The spelling of 21987040 in words is "twenty-one million, nine hundred eighty-seven thousand, forty".