21513423 has 8 divisors (see below), whose sum is σ = 28875136. Its totient is φ = 14247000.

The previous prime is 21513413. The next prime is 21513433. The reversal of 21513423 is 32431512.

It is an interprime number because it is at equal distance from previous prime (21513413) and next prime (21513433).

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

It is a de Polignac number, because none of the positive numbers 2^k-21513423 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 21513423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513403) 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, 23293 + ... + 24198.

It is an arithmetic number, because the mean of its divisors is an integer number (3609392).

Almost surely, 2^21513423 is an apocalyptic number.

21513423 is a deficient number, since it is larger than the sum of its proper divisors (7361713).

21513423 is a wasteful number, since it uses less digits than its factorization.

21513423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47645.

The product of its digits is 720, while the sum is 21.

The square root of 21513423 is about 4638.2564612147. The cubic root of 21513423 is about 278.1227439618.

Adding to 21513423 its reverse (32431512), we get a palindrome (53944935).

The spelling of 21513423 in words is "twenty-one million, five hundred thirteen thousand, four hundred twenty-three".