21245705 has 16 divisors (see below), whose sum is σ = 28902720. Its totient is φ = 14862528.

The previous prime is 21245683. The next prime is 21245713. The reversal of 21245705 is 50754212.

It is a cyclic number.

It is not a de Polignac number, because 21245705 - 2¹⁰ = 21244681 is a prime.

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, 7367 + ... + 9836.

It is an arithmetic number, because the mean of its divisors is an integer number (1806420).

Almost surely, 2^21245705 is an apocalyptic number.

It is an amenable number.

21245705 is a deficient number, since it is larger than the sum of its proper divisors (7657015).

21245705 is a wasteful number, since it uses less digits than its factorization.

21245705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17240.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21245705 is about 4609.3063469464. The cubic root of 21245705 is about 276.9642505355.

Adding to 21245705 its reverse (50754212), we get a palindrome (71999917).

The spelling of 21245705 in words is "twenty-one million, two hundred forty-five thousand, seven hundred five".