21534391 has 8 divisors (see below), whose sum is σ = 22716800. Its totient is φ = 20356920.

The previous prime is 21534349. The next prime is 21534397. The reversal of 21534391 is 19343512.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21534391 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 (21534397) 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 7 ways as a sum of consecutive naturals, for example, 10846 + ... + 12676.

It is an arithmetic number, because the mean of its divisors is an integer number (2839600).

Almost surely, 2^21534391 is an apocalyptic number.

21534391 is a deficient number, since it is larger than the sum of its proper divisors (1182409).

21534391 is a wasteful number, since it uses less digits than its factorization.

21534391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2469.

The product of its digits is 3240, while the sum is 28.

The square root of 21534391 is about 4640.5162428333. The cubic root of 21534391 is about 278.2130718176.

It can be divided in two parts, 21 and 534391, that multiplied together give a palindrome (11222211).

The spelling of 21534391 in words is "twenty-one million, five hundred thirty-four thousand, three hundred ninety-one".