21087396 has 108 divisors (see below), whose sum is σ = 60418176. Its totient is φ = 6193440.

The previous prime is 21087377. The next prime is 21087401. The reversal of 21087396 is 69378012.

21087396 = 356² + 357² + ... + 476².

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21087396.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 204681 + ... + 204783.

It is a vampire number, since it can be written as 3102 ⋅ 6798 (with its own digits).

Almost surely, 2^21087396 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21087396, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30209088).

21087396 is an abundant number, since it is smaller than the sum of its proper divisors (39330780).

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

21087396 is a wasteful number, since it uses less digits than its factorization.

21087396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21087396 is about 4592.1014797149. The cubic root of 21087396 is about 276.2746163987.

The spelling of 21087396 in words is "twenty-one million, eighty-seven thousand, three hundred ninety-six".