21621444 has 24 divisors (see below), whose sum is σ = 54331200. Its totient is φ = 6652704.

The previous prime is 21621437. The next prime is 21621463. The reversal of 21621444 is 44412612.

It is a happy number.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69144 + ... + 69455.

It is an arithmetic number, because the mean of its divisors is an integer number (2263800).

Almost surely, 2^21621444 is an apocalyptic number.

It is an amenable number.

21621444 is an abundant number, since it is smaller than the sum of its proper divisors (32709756).

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

21621444 is a wasteful number, since it uses less digits than its factorization.

21621444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138619 (or 138617 counting only the distinct ones).

The product of its digits is 1536, while the sum is 24.

The square root of 21621444 is about 4649.8864502265. The cubic root of 21621444 is about 278.5874608600.

The spelling of 21621444 in words is "twenty-one million, six hundred twenty-one thousand, four hundred forty-four".