21055240 has 16 divisors (see below), whose sum is σ = 47374380. Its totient is φ = 8422080.

The previous prime is 21055217. The next prime is 21055259. The reversal of 21055240 is 4255012.

It can be written as a sum of positive squares in 2 ways, for example, as 20994724 + 60516 = 4582^2 + 246^2 .

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, 263151 + ... + 263230.

Almost surely, 2^21055240 is an apocalyptic number.

21055240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21055240 is an abundant number, since it is smaller than the sum of its proper divisors (26319140).

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

21055240 is a wasteful number, since it uses less digits than its factorization.

21055240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 526392 (or 526388 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21055240 is about 4588.5989147015. The cubic root of 21055240 is about 276.1341153137.

The spelling of 21055240 in words is "twenty-one million, fifty-five thousand, two hundred forty".