21034391 has 4 divisors (see below), whose sum is σ = 24039312. Its totient is φ = 18029472.

The previous prime is 21034369. The next prime is 21034411. The reversal of 21034391 is 19343012.

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 21034391 - 2¹⁰ = 21033367 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 (21034301) 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, 1502450 + ... + 1502463.

It is an arithmetic number, because the mean of its divisors is an integer number (6009828).

Almost surely, 2^21034391 is an apocalyptic number.

21034391 is a deficient number, since it is larger than the sum of its proper divisors (3004921).

21034391 is an equidigital number, since it uses as much as digits as its factorization.

21034391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3004920.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 21034391 is about 4586.3265256630. The cubic root of 21034391 is about 276.0429421037.

The spelling of 21034391 in words is "twenty-one million, thirty-four thousand, three hundred ninety-one".