21689613 has 30 divisors (see below), whose sum is σ = 35629902. Its totient is φ = 13139280.

The previous prime is 21689611. The next prime is 21689617. The reversal of 21689613 is 31698612.

It can be written as a sum of positive squares in only one way, i.e., 21650409 + 39204 = 4653^2 + 198^2 .

It is not a de Polignac number, because 21689613 - 2¹ = 21689611 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21689611) 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 29 ways as a sum of consecutive naturals, for example, 8695 + ... + 10907.

Almost surely, 2^21689613 is an apocalyptic number.

It is an amenable number.

21689613 is a deficient number, since it is larger than the sum of its proper divisors (13940289).

21689613 is a wasteful number, since it uses less digits than its factorization.

21689613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2247 (or 2227 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 21689613 is about 4657.2108605903. The cubic root of 21689613 is about 278.8799344637.

It can be divided in two parts, 2168 and 9613, that added together give a triangular number (11781 = T₁₅₃).

The spelling of 21689613 in words is "twenty-one million, six hundred eighty-nine thousand, six hundred thirteen".