21782087 has 4 divisors (see below), whose sum is σ = 21822456. Its totient is φ = 21741720.

The previous prime is 21782071. The next prime is 21782107. The reversal of 21782087 is 78028712.

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 21782087 - 2⁴ = 21782071 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 (21782017) 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 3 ways as a sum of consecutive naturals, for example, 19364 + ... + 20457.

It is an arithmetic number, because the mean of its divisors is an integer number (5455614).

Almost surely, 2^21782087 is an apocalyptic number.

21782087 is a deficient number, since it is larger than the sum of its proper divisors (40369).

21782087 is an equidigital number, since it uses as much as digits as its factorization.

21782087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40368.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 21782087 is about 4667.1283462103. The cubic root of 21782087 is about 279.2757088346.

The spelling of 21782087 in words is "twenty-one million, seven hundred eighty-two thousand, eighty-seven".