21783691 has 6 divisors (see below), whose sum is σ = 22772540. Its totient is φ = 20836068.

The previous prime is 21783683. The next prime is 21783703. The reversal of 21783691 is 19638712.

It is not a de Polignac number, because 21783691 - 2³ = 21783683 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21783691.

It is not an unprimeable number, because it can be changed into a prime (21783631) 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 5 ways as a sum of consecutive naturals, for example, 20061 + ... + 21118.

Almost surely, 2^21783691 is an apocalyptic number.

21783691 is a deficient number, since it is larger than the sum of its proper divisors (988849).

21783691 is an equidigital number, since it uses as much as digits as its factorization.

21783691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41225 (or 41202 counting only the distinct ones).

The product of its digits is 18144, while the sum is 37.

The square root of 21783691 is about 4667.3001831894. The cubic root of 21783691 is about 279.2825638135.

The spelling of 21783691 in words is "twenty-one million, seven hundred eighty-three thousand, six hundred ninety-one".