21252705 has 16 divisors (see below), whose sum is σ = 34563264. Its totient is φ = 11148480.

The previous prime is 21252691. The next prime is 21252727. The reversal of 21252705 is 50725212.

It is not a de Polignac number, because 21252705 - 2¹⁵ = 21219937 is a prime.

It is an alternating number because its digits alternate between even and odd.

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, 10699 + ... + 12528.

It is an arithmetic number, because the mean of its divisors is an integer number (2160204).

Almost surely, 2^21252705 is an apocalyptic number.

It is an amenable number.

21252705 is a deficient number, since it is larger than the sum of its proper divisors (13310559).

21252705 is a wasteful number, since it uses less digits than its factorization.

21252705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23296.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21252705 is about 4610.0656177543. The cubic root of 21252705 is about 276.9946651042.

Adding to 21252705 its reverse (50725212), we get a palindrome (71977917).

The spelling of 21252705 in words is "twenty-one million, two hundred fifty-two thousand, seven hundred five".