21568051 has 4 divisors (see below), whose sum is σ = 21646192. Its totient is φ = 21489912.

The previous prime is 21568049. The next prime is 21568067. The reversal of 21568051 is 15086512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21568051 - 2¹ = 21568049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21568031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38655 + ... + 39208.

It is an arithmetic number, because the mean of its divisors is an integer number (5411548).

Almost surely, 2^21568051 is an apocalyptic number.

21568051 is a deficient number, since it is larger than the sum of its proper divisors (78141).

21568051 is an equidigital number, since it uses as much as digits as its factorization.

21568051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78140.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21568051 is about 4644.1415783759. The cubic root of 21568051 is about 278.3579528902.

The spelling of 21568051 in words is "twenty-one million, five hundred sixty-eight thousand, fifty-one".