21985940 has 24 divisors (see below), whose sum is σ = 46284000. Its totient is φ = 8772768.

The previous prime is 21985939. The next prime is 21985949. The reversal of 21985940 is 4958912.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21985894 and 21985903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21985949) 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, 8879 + ... + 11081.

It is an arithmetic number, because the mean of its divisors is an integer number (1928500).

Almost surely, 2^21985940 is an apocalyptic number.

21985940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21985940 is an abundant number, since it is smaller than the sum of its proper divisors (24298060).

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

21985940 is a wasteful number, since it uses less digits than its factorization.

21985940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2711 (or 2709 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 21985940 is about 4688.9167192434. The cubic root of 21985940 is about 280.1442284161.

The spelling of 21985940 in words is "twenty-one million, nine hundred eighty-five thousand, nine hundred forty".