21005072 has 40 divisors (see below), whose sum is σ = 46336320. Its totient is φ = 9130880.

The previous prime is 21005069. The next prime is 21005087. The reversal of 21005072 is 27050012.

It is a self number, because there is not a number n which added to its sum of digits gives 21005072.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1454 + ... + 6642.

It is an arithmetic number, because the mean of its divisors is an integer number (1158408).

Almost surely, 2^21005072 is an apocalyptic number.

21005072 is a gapful number since it is divisible by the number (22) 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 21005072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23168160).

21005072 is an abundant number, since it is smaller than the sum of its proper divisors (25331248).

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

21005072 is a wasteful number, since it uses less digits than its factorization.

21005072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5231 (or 5225 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 21005072 is about 4583.1290621147. The cubic root of 21005072 is about 275.9146273794.

Adding to 21005072 its reverse (27050012), we get a palindrome (48055084).

The spelling of 21005072 in words is "twenty-one million, five thousand, seventy-two".