21945140 has 60 divisors (see below), whose sum is σ = 53880036. Its totient is φ = 7507584.

The previous prime is 21945137. The next prime is 21945149. The reversal of 21945140 is 4154912.

It can be written as a sum of positive squares in 2 ways, for example, as 13868176 + 8076964 = 3724^2 + 2842^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21945149) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 47792 + ... + 48248.

Almost surely, 2^21945140 is an apocalyptic number.

21945140 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 21945140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26940018).

21945140 is an abundant number, since it is smaller than the sum of its proper divisors (31934896).

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

21945140 is an equidigital number, since it uses as much as digits as its factorization.

21945140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494 (or 471 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21945140 is about 4684.5640138651. The cubic root of 21945140 is about 279.9708302946.

The spelling of 21945140 in words is "twenty-one million, nine hundred forty-five thousand, one hundred forty".