21561285 has 16 divisors (see below), whose sum is σ = 35340480. Its totient is φ = 11218560.

The previous prime is 21561277. The next prime is 21561311. The reversal of 21561285 is 58216512.

It is not a de Polignac number, because 21561285 - 2³ = 21561277 is a prime.

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, 16915 + ... + 18144.

It is an arithmetic number, because the mean of its divisors is an integer number (2208780).

Almost surely, 2^21561285 is an apocalyptic number.

It is an amenable number.

21561285 is a deficient number, since it is larger than the sum of its proper divisors (13779195).

21561285 is a wasteful number, since it uses less digits than its factorization.

21561285 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35108.

The product of its digits is 4800, while the sum is 30.

The square root of 21561285 is about 4643.4130766065. The cubic root of 21561285 is about 278.3288424421.

Adding to 21561285 its reverse (58216512), we get a palindrome (79777797).

The spelling of 21561285 in words is "twenty-one million, five hundred sixty-one thousand, two hundred eighty-five".