21455240 has 32 divisors (see below), whose sum is σ = 48406680. Its totient is φ = 8558592.

The previous prime is 21455183. The next prime is 21455257. The reversal of 21455240 is 4255412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 15413476 + 6041764 = 3926^2 + 2458^2 .

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, 26522 + ... + 27318.

Almost surely, 2^21455240 is an apocalyptic number.

21455240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21455240 is an abundant number, since it is smaller than the sum of its proper divisors (26951440).

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

21455240 is a wasteful number, since it uses less digits than its factorization.

21455240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1481 (or 1477 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21455240 is about 4631.9801381267. The cubic root of 21455240 is about 277.8717901636.

The spelling of 21455240 in words is "twenty-one million, four hundred fifty-five thousand, two hundred forty".