21287260 has 24 divisors (see below), whose sum is σ = 44873136. Its totient is φ = 8482560.

The previous prime is 21287251. The next prime is 21287263. The reversal of 21287260 is 6278212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3780 + ... + 7540.

It is an arithmetic number, because the mean of its divisors is an integer number (1869714).

Almost surely, 2^21287260 is an apocalyptic number.

21287260 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21287260 is an abundant number, since it is smaller than the sum of its proper divisors (23585876).

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

21287260 is a wasteful number, since it uses less digits than its factorization.

21287260 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4053 (or 4051 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 21287260 is about 4613.8118730611. The cubic root of 21287260 is about 277.1447066768.

The spelling of 21287260 in words is "twenty-one million, two hundred eighty-seven thousand, two hundred sixty".