21155072 has 36 divisors (see below), whose sum is σ = 44720676. Its totient is φ = 9953280.

The previous prime is 21155053. The next prime is 21155087. The reversal of 21155072 is 27055112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 18113536 + 3041536 = 4256^2 + 1744^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1922 + ... + 6782.

It is an arithmetic number, because the mean of its divisors is an integer number (1242241).

Almost surely, 2^21155072 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 21155072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22360338).

21155072 is an abundant number, since it is smaller than the sum of its proper divisors (23565604).

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

21155072 is an equidigital number, since it uses as much as digits as its factorization.

21155072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4894 (or 4880 counting only the distinct ones).

The product of its (nonzero) digits is 700, while the sum is 23.

The square root of 21155072 is about 4599.4643166351. The cubic root of 21155072 is about 276.5698511266.

The spelling of 21155072 in words is "twenty-one million, one hundred fifty-five thousand, seventy-two".