21173240 has 32 divisors (see below), whose sum is σ = 51971760. Its totient is φ = 7699200.

The previous prime is 21173233. The next prime is 21173263. The reversal of 21173240 is 4237112.

It is a super-3 number, since 3×21173240³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

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, 23621 + ... + 24500.

Almost surely, 2^21173240 is an apocalyptic number.

21173240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21173240 is an abundant number, since it is smaller than the sum of its proper divisors (30798520).

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

21173240 is a wasteful number, since it uses less digits than its factorization.

21173240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48143 (or 48139 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21173240 is about 4601.4389053860. The cubic root of 21173240 is about 276.6490013075.

The spelling of 21173240 in words is "twenty-one million, one hundred seventy-three thousand, two hundred forty".