21705234 has 16 divisors (see below), whose sum is σ = 43457472. Its totient is φ = 7227248.

The previous prime is 21705227. The next prime is 21705241. The reversal of 21705234 is 43250712.

It is an interprime number because it is at equal distance from previous prime (21705227) and next prime (21705241).

It is a super-2 number, since 2×21705234² = 942234365989512, which contains 22 as substring.

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, 7747 + ... + 10169.

It is an arithmetic number, because the mean of its divisors is an integer number (2716092).

Almost surely, 2^21705234 is an apocalyptic number.

21705234 is an abundant number, since it is smaller than the sum of its proper divisors (21752238).

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

21705234 is a wasteful number, since it uses less digits than its factorization.

21705234 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3921.

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21705234 is about 4658.8876354769. The cubic root of 21705234 is about 278.9468687768.

Adding to 21705234 its reverse (43250712), we get a palindrome (64955946).

The spelling of 21705234 in words is "twenty-one million, seven hundred five thousand, two hundred thirty-four".