21539700 has 216 divisors, whose sum is σ = 83411328. Its totient is φ = 4527360.

The previous prime is 21539681. The next prime is 21539701. The reversal of 21539700 is 793512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21539701) 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, 81769 + ... + 82031.

Almost surely, 2^21539700 is an apocalyptic number.

21539700 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 21539700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41705664).

21539700 is an abundant number, since it is smaller than the sum of its proper divisors (61871628).

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

21539700 is a wasteful number, since it uses less digits than its factorization.

21539700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303 (or 293 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21539700 is about 4641.0882344554. The cubic root of 21539700 is about 278.2359331070.

The spelling of 21539700 in words is "twenty-one million, five hundred thirty-nine thousand, seven hundred".