21985040 has 160 divisors (see below), whose sum is σ = 65995776. Its totient is φ = 6612480.

The previous prime is 21985039. The next prime is 21985043. The reversal of 21985040 is 4058912.

It is a junction number, because it is equal to n+sod(n) for n = 21984994 and 21985012.

It is not an unprimeable number, because it can be changed into a prime (21985043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 264839 + ... + 264921.

Almost surely, 2^21985040 is an apocalyptic number.

21985040 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 21985040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32997888).

21985040 is an abundant number, since it is smaller than the sum of its proper divisors (44010736).

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

21985040 is a wasteful number, since it uses less digits than its factorization.

21985040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157 (or 151 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 21985040 is about 4688.8207472668. The cubic root of 21985040 is about 280.1404057723.

The spelling of 21985040 in words is "twenty-one million, nine hundred eighty-five thousand, forty".