21560551 has 4 divisors (see below), whose sum is σ = 21570192. Its totient is φ = 21550912.

The previous prime is 21560549. The next prime is 21560557. The reversal of 21560551 is 15506512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21560551 - 2¹ = 21560549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21560557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 471 + ... + 6583.

It is an arithmetic number, because the mean of its divisors is an integer number (5392548).

Almost surely, 2^21560551 is an apocalyptic number.

21560551 is a deficient number, since it is larger than the sum of its proper divisors (9641).

21560551 is an equidigital number, since it uses as much as digits as its factorization.

21560551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9640.

The product of its (nonzero) digits is 1500, while the sum is 25.

The square root of 21560551 is about 4643.3340392438. The cubic root of 21560551 is about 278.3256840699.

The spelling of 21560551 in words is "twenty-one million, five hundred sixty thousand, five hundred fifty-one".