21705330 has 64 divisors (see below), whose sum is σ = 55157760. Its totient is φ = 5455296.

The previous prime is 21705323. The next prime is 21705337. The reversal of 21705330 is 3350712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21705323) and next prime (21705337).

It is a super-2 number, since 2×21705330² = 942242700817800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21705297 and 21705306.

It is not an unprimeable number, because it can be changed into a prime (21705337) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 57081 + ... + 57459.

It is an arithmetic number, because the mean of its divisors is an integer number (861840).

Almost surely, 2^21705330 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21705330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27578880).

21705330 is an abundant number, since it is smaller than the sum of its proper divisors (33452430).

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

21705330 is a wasteful number, since it uses less digits than its factorization.

21705330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495.

The product of its (nonzero) digits is 630, while the sum is 21.

The square root of 21705330 is about 4658.8979383541. The cubic root of 21705330 is about 278.9472800272.

The spelling of 21705330 in words is "twenty-one million, seven hundred five thousand, three hundred thirty".