21750861 has 16 divisors (see below), whose sum is σ = 32074560. Its totient is φ = 13000320.

The previous prime is 21750851. The next prime is 21750863. The reversal of 21750861 is 16805712.

It is not a de Polignac number, because 21750861 - 2⁶ = 21750797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21750863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2106 + ... + 6923.

It is an arithmetic number, because the mean of its divisors is an integer number (2004660).

Almost surely, 2^21750861 is an apocalyptic number.

It is an amenable number.

21750861 is a deficient number, since it is larger than the sum of its proper divisors (10323699).

21750861 is a wasteful number, since it uses less digits than its factorization.

21750861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9116.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21750861 is about 4663.7818345201. The cubic root of 21750861 is about 279.1421918792.

The spelling of 21750861 in words is "twenty-one million, seven hundred fifty thousand, eight hundred sixty-one".