21725240 has 16 divisors (see below), whose sum is σ = 48881880. Its totient is φ = 8690080.

The previous prime is 21725239. The next prime is 21725273. The reversal of 21725240 is 4252712.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271526 + ... + 271605.

Almost surely, 2^21725240 is an apocalyptic number.

21725240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21725240 is an abundant number, since it is smaller than the sum of its proper divisors (27156640).

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

21725240 is a wasteful number, since it uses less digits than its factorization.

21725240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 543142 (or 543138 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21725240 is about 4661.0342199988. The cubic root of 21725240 is about 279.0325454598.

Adding to 21725240 its reverse (4252712), we get a palindrome (25977952).

The spelling of 21725240 in words is "twenty-one million, seven hundred twenty-five thousand, two hundred forty".