21281613 has 8 divisors (see below), whose sum is σ = 28396800. Its totient is φ = 14177088.

The previous prime is 21281599. The next prime is 21281627. The reversal of 21281613 is 31618212.

It is an interprime number because it is at equal distance from previous prime (21281599) and next prime (21281627).

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

It is not a de Polignac number, because 21281613 - 2⁵ = 21281581 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21281683) 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, 6468 + ... + 9186.

It is an arithmetic number, because the mean of its divisors is an integer number (3549600).

Almost surely, 2^21281613 is an apocalyptic number.

It is an amenable number.

21281613 is a deficient number, since it is larger than the sum of its proper divisors (7115187).

21281613 is a wasteful number, since it uses less digits than its factorization.

21281613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5331.

The product of its digits is 576, while the sum is 24.

The square root of 21281613 is about 4613.1998656031. The cubic root of 21281613 is about 277.1201978929.

Adding to 21281613 its reverse (31618212), we get a palindrome (52899825).

It can be divided in two parts, 2128 and 1613, that added together give a triangular number (3741 = T₈₆).

The spelling of 21281613 in words is "twenty-one million, two hundred eighty-one thousand, six hundred thirteen".