21644454 has 16 divisors (see below), whose sum is σ = 46618992. Its totient is φ = 6659808.

The previous prime is 21644429. The next prime is 21644459. The reversal of 21644454 is 45444612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644459) 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, 138669 + ... + 138824.

It is an arithmetic number, because the mean of its divisors is an integer number (2913687).

Almost surely, 2^21644454 is an apocalyptic number.

21644454 is an abundant number, since it is smaller than the sum of its proper divisors (24974538).

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

21644454 is a wasteful number, since it uses less digits than its factorization.

21644454 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277511.

The product of its digits is 15360, while the sum is 30.

The square root of 21644454 is about 4652.3600462561. The cubic root of 21644454 is about 278.6862520543.

The spelling of 21644454 in words is "twenty-one million, six hundred forty-four thousand, four hundred fifty-four".