21308613 has 8 divisors (see below), whose sum is σ = 28835808. Its totient is φ = 13993584.

The previous prime is 21308611. The next prime is 21308629. The reversal of 21308613 is 31680312.

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

It is not a de Polignac number, because 21308613 - 2¹ = 21308611 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52806 + ... + 53207.

It is an arithmetic number, because the mean of its divisors is an integer number (3604476).

Almost surely, 2^21308613 is an apocalyptic number.

It is an amenable number.

21308613 is a deficient number, since it is larger than the sum of its proper divisors (7527195).

21308613 is a wasteful number, since it uses less digits than its factorization.

21308613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106083.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21308613 is about 4616.1253232554. The cubic root of 21308613 is about 277.2373425743.

Adding to 21308613 its reverse (31680312), we get a palindrome (52988925).

The spelling of 21308613 in words is "twenty-one million, three hundred eight thousand, six hundred thirteen".