21085272 has 80 divisors (see below), whose sum is σ = 63626640. Its totient is φ = 6485184.

The previous prime is 21085271. The next prime is 21085277. The reversal of 21085272 is 27258012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085271) by changing a digit.

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 19 ways as a sum of consecutive naturals, for example, 7173 + ... + 9675.

It is an arithmetic number, because the mean of its divisors is an integer number (795333).

Almost surely, 2^21085272 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 21085272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31813320).

21085272 is an abundant number, since it is smaller than the sum of its proper divisors (42541368).

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

21085272 is a wasteful number, since it uses less digits than its factorization.

21085272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2534 (or 2521 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21085272 is about 4591.8702072249. The cubic root of 21085272 is about 276.2653402891.

It can be divided in two parts, 210 and 85272, that multiplied together give a triangular number (17907120 = T₅₉₈₄).

The spelling of 21085272 in words is "twenty-one million, eighty-five thousand, two hundred seventy-two".