21992240 has 40 divisors (see below), whose sum is σ = 52228800. Its totient is φ = 8608256.

The previous prime is 21992239. The next prime is 21992249. The reversal of 21992240 is 4229912.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21992249) 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, 836 + ... + 6684.

It is an arithmetic number, because the mean of its divisors is an integer number (1305720).

Almost surely, 2^21992240 is an apocalyptic number.

21992240 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 21992240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26114400).

21992240 is an abundant number, since it is smaller than the sum of its proper divisors (30236560).

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

21992240 is a wasteful number, since it uses less digits than its factorization.

21992240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5909 (or 5903 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21992240 is about 4689.5884680854. The cubic root of 21992240 is about 280.1709840015.

The spelling of 21992240 in words is "twenty-one million, nine hundred ninety-two thousand, two hundred forty".