21538444 has 6 divisors (see below), whose sum is σ = 37692284. Its totient is φ = 10769220.

The previous prime is 21538427. The next prime is 21538453. The reversal of 21538444 is 44483512.

It is a super-2 number, since 2×21538444² = 927809139882272, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2692302 + ... + 2692309.

Almost surely, 2^21538444 is an apocalyptic number.

It is an amenable number.

21538444 is a deficient number, since it is larger than the sum of its proper divisors (16153840).

21538444 is a wasteful number, since it uses less digits than its factorization.

21538444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5384615 (or 5384613 counting only the distinct ones).

The product of its digits is 15360, while the sum is 31.

The square root of 21538444 is about 4640.9529193906. The cubic root of 21538444 is about 278.2305249363.

The spelling of 21538444 in words is "twenty-one million, five hundred thirty-eight thousand, four hundred forty-four".