21287860 has 24 divisors (see below), whose sum is σ = 48769056. Its totient is φ = 7740960.

The previous prime is 21287837. The next prime is 21287869. The reversal of 21287860 is 6878212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48162 + ... + 48601.

It is an arithmetic number, because the mean of its divisors is an integer number (2032044).

Almost surely, 2^21287860 is an apocalyptic number.

21287860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21287860 is an abundant number, since it is smaller than the sum of its proper divisors (27481196).

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

21287860 is a wasteful number, since it uses less digits than its factorization.

21287860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96783 (or 96781 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 21287860 is about 4613.8768947600. The cubic root of 21287860 is about 277.1473105075.

The spelling of 21287860 in words is "twenty-one million, two hundred eighty-seven thousand, eight hundred sixty".