21705270 has 32 divisors (see below), whose sum is σ = 53775360. Its totient is φ = 5601120.

The previous prime is 21705269. The next prime is 21705289. The reversal of 21705270 is 7250712.

It is a super-2 number, since 2×21705270² = 942237491545800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21705270.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10740 + ... + 12599.

It is an arithmetic number, because the mean of its divisors is an integer number (1680480).

Almost surely, 2^21705270 is an apocalyptic number.

21705270 is an abundant number, since it is smaller than the sum of its proper divisors (32070090).

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

21705270 is a wasteful number, since it uses less digits than its factorization.

21705270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23380.

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 21705270 is about 4658.8914990585. The cubic root of 21705270 is about 278.9470229958.

Adding to 21705270 its reverse (7250712), we get a palindrome (28955982).

The spelling of 21705270 in words is "twenty-one million, seven hundred five thousand, two hundred seventy".