21887861 has 4 divisors (see below), whose sum is σ = 21978924. Its totient is φ = 21796800.

The previous prime is 21887851. The next prime is 21887893. The reversal of 21887861 is 16878812.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15288100 + 6599761 = 3910^2 + 2569^2 .

It is a cyclic number.

It is not a de Polignac number, because 21887861 - 2⁶ = 21887797 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 (21887821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45170 + ... + 45651.

It is an arithmetic number, because the mean of its divisors is an integer number (5494731).

Almost surely, 2^21887861 is an apocalyptic number.

It is an amenable number.

21887861 is a deficient number, since it is larger than the sum of its proper divisors (91063).

21887861 is an equidigital number, since it uses as much as digits as its factorization.

21887861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91062.

The product of its digits is 43008, while the sum is 41.

The square root of 21887861 is about 4678.4464301732. The cubic root of 21887861 is about 279.7270341481.

The spelling of 21887861 in words is "twenty-one million, eight hundred eighty-seven thousand, eight hundred sixty-one".