21287100 has 36 divisors (see below), whose sum is σ = 61591544. Its totient is φ = 5676480.

The previous prime is 21287089. The next prime is 21287129. The reversal of 21287100 is 178212.

It is a congruent number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 35179 + ... + 35778.

Almost surely, 2^21287100 is an apocalyptic number.

21287100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21287100 is an abundant number, since it is smaller than the sum of its proper divisors (40304444).

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

21287100 is a wasteful number, since it uses less digits than its factorization.

21287100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70974 (or 70967 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 21287100 is about 4613.7945337867. The cubic root of 21287100 is about 277.1440123137.

The spelling of 21287100 in words is "twenty-one million, two hundred eighty-seven thousand, one hundred".