21173440 has 56 divisors (see below), whose sum is σ = 50913792. Its totient is φ = 8386560.

The previous prime is 21173437. The next prime is 21173473. The reversal of 21173440 is 4437112.

It is a super-2 number, since 2×21173440² = 896629122867200, which contains 22 as substring.

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, 40380 + ... + 40900.

Almost surely, 2^21173440 is an apocalyptic number.

21173440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21173440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25456896).

21173440 is an abundant number, since it is smaller than the sum of its proper divisors (29740352).

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

21173440 is a wasteful number, since it uses less digits than its factorization.

21173440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665 (or 655 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 21173440 is about 4601.4606376671. The cubic root of 21173440 is about 276.6498723697.

The spelling of 21173440 in words is "twenty-one million, one hundred seventy-three thousand, four hundred forty".