21001613 has 4 divisors (see below), whose sum is σ = 22237020. Its totient is φ = 19766208.

The previous prime is 21001577. The next prime is 21001627. The reversal of 21001613 is 31610012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16662724 + 4338889 = 4082^2 + 2083^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001613 - 2⁶ = 21001549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001693) 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 3 ways as a sum of consecutive naturals, for example, 617678 + ... + 617711.

It is an arithmetic number, because the mean of its divisors is an integer number (5559255).

Almost surely, 2^21001613 is an apocalyptic number.

It is an amenable number.

21001613 is a deficient number, since it is larger than the sum of its proper divisors (1235407).

21001613 is a wasteful number, since it uses less digits than its factorization.

21001613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1235406.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 21001613 is about 4582.7516843050. The cubic root of 21001613 is about 275.8994811790.

Adding to 21001613 its reverse (31610012), we get a palindrome (52611625).

The spelling of 21001613 in words is "twenty-one million, one thousand, six hundred thirteen".