21433640 has 32 divisors (see below), whose sum is σ = 48547080. Its totient is φ = 8516352.

The previous prime is 21433613. The next prime is 21433649. The reversal of 21433640 is 4633412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 19589476 + 1844164 = 4426^2 + 1358^2 .

It is not an unprimeable number, because it can be changed into a prime (21433649) 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, 4574 + ... + 7986.

Almost surely, 2^21433640 is an apocalyptic number.

21433640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21433640 is an abundant number, since it is smaller than the sum of its proper divisors (27113440).

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

21433640 is a wasteful number, since it uses less digits than its factorization.

21433640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3581 (or 3577 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 23.

The square root of 21433640 is about 4629.6479347786. The cubic root of 21433640 is about 277.7785099833.

The spelling of 21433640 in words is "twenty-one million, four hundred thirty-three thousand, six hundred forty".