21013391 has 8 divisors (see below), whose sum is σ = 24080160. Its totient is φ = 17962848.

The previous prime is 21013379. The next prime is 21013397. The reversal of 21013391 is 19331012.

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

It is a cyclic number.

It is not a de Polignac number, because 21013391 - 2¹⁰ = 21012367 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 (21013397) 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, 1136 + ... + 6581.

It is an arithmetic number, because the mean of its divisors is an integer number (3010020).

Almost surely, 2^21013391 is an apocalyptic number.

21013391 is a deficient number, since it is larger than the sum of its proper divisors (3066769).

21013391 is an equidigital number, since it uses as much as digits as its factorization.

21013391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8113.

The product of its (nonzero) digits is 162, while the sum is 20.

The square root of 21013391 is about 4584.0365399940. The cubic root of 21013391 is about 275.9510476438.

The spelling of 21013391 in words is "twenty-one million, thirteen thousand, three hundred ninety-one".