21861611 has 4 divisors (see below), whose sum is σ = 21874272. Its totient is φ = 21848952.

The previous prime is 21861601. The next prime is 21861649. The reversal of 21861611 is 11616812.

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 21861611 - 2⁶ = 21861547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21861601) 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, 3236 + ... + 7361.

It is an arithmetic number, because the mean of its divisors is an integer number (5468568).

Almost surely, 2^21861611 is an apocalyptic number.

21861611 is a deficient number, since it is larger than the sum of its proper divisors (12661).

21861611 is a wasteful number, since it uses less digits than its factorization.

21861611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12660.

The product of its digits is 576, while the sum is 26.

The square root of 21861611 is about 4675.6401700730. The cubic root of 21861611 is about 279.6151643464.

The spelling of 21861611 in words is "twenty-one million, eight hundred sixty-one thousand, six hundred eleven".