21953440 has 24 divisors (see below), whose sum is σ = 51865380. Its totient is φ = 8781312.

The previous prime is 21953419. The next prime is 21953447. The reversal of 21953440 is 4435912.

It can be written as a sum of positive squares in 2 ways, for example, as 21790224 + 163216 = 4668^2 + 404^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21953399 and 21953408.

It is not an unprimeable number, because it can be changed into a prime (21953447) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68445 + ... + 68764.

Almost surely, 2^21953440 is an apocalyptic number.

21953440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21953440 is an abundant number, since it is smaller than the sum of its proper divisors (29911940).

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

21953440 is a wasteful number, since it uses less digits than its factorization.

21953440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137224 (or 137216 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21953440 is about 4685.4498183205. The cubic root of 21953440 is about 280.0061223151.

The spelling of 21953440 in words is "twenty-one million, nine hundred fifty-three thousand, four hundred forty".