21287700 has 216 divisors, whose sum is σ = 79439360. Its totient is φ = 4665600.

The previous prime is 21287681. The next prime is 21287701. The reversal of 21287700 is 778212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287701) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 195246 + ... + 195354.

Almost surely, 2^21287700 is an apocalyptic number.

21287700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21287700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39719680).

21287700 is an abundant number, since it is smaller than the sum of its proper divisors (58151660).

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

21287700 is a wasteful number, since it uses less digits than its factorization.

21287700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167 (or 157 counting only the distinct ones).

The product of its (nonzero) digits is 1568, while the sum is 27.

The square root of 21287700 is about 4613.8595557299. The cubic root of 21287700 is about 277.1466161574.

The spelling of 21287700 in words is "twenty-one million, two hundred eighty-seven thousand, seven hundred".