20405240 has 32 divisors (see below), whose sum is σ = 48330000. Its totient is φ = 7732224.

The previous prime is 20405239. The next prime is 20405251. The reversal of 20405240 is 4250402.

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, 12665 + ... + 14184.

Almost surely, 2^20405240 is an apocalyptic number.

20405240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20405240 is an abundant number, since it is smaller than the sum of its proper divisors (27924760).

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

20405240 is a wasteful number, since it uses less digits than its factorization.

20405240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26879 (or 26875 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 17.

The square root of 20405240 is about 4517.2159567592. The cubic root of 20405240 is about 273.2628346176.

Adding to 20405240 its reverse (4250402), we get a palindrome (24655642).

The spelling of 20405240 in words is "twenty million, four hundred five thousand, two hundred forty".