21082391 has 8 divisors (see below), whose sum is σ = 23792400. Its totient is φ = 18504640.

The previous prime is 21082361. The next prime is 21082403. The reversal of 21082391 is 19328012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21082391 - 2¹⁴ = 21066007 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 21082391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21082301) 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 7 ways as a sum of consecutive naturals, for example, 32726 + ... + 33363.

It is an arithmetic number, because the mean of its divisors is an integer number (2974050).

Almost surely, 2^21082391 is an apocalyptic number.

21082391 is a deficient number, since it is larger than the sum of its proper divisors (2710009).

21082391 is a wasteful number, since it uses less digits than its factorization.

21082391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66129.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21082391 is about 4591.5564899062. The cubic root of 21082391 is about 276.2527571505.

The spelling of 21082391 in words is "twenty-one million, eighty-two thousand, three hundred ninety-one".