21011913 has 16 divisors (see below), whose sum is σ = 33523840. Its totient is φ = 12930192.

The previous prime is 21011873. The next prime is 21011917. The reversal of 21011913 is 31911012.

It is not a de Polignac number, because 21011913 - 2¹⁰ = 21010889 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21011917) 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 15 ways as a sum of consecutive naturals, for example, 29581 + ... + 30282.

It is an arithmetic number, because the mean of its divisors is an integer number (2095240).

Almost surely, 2^21011913 is an apocalyptic number.

It is an amenable number.

21011913 is a deficient number, since it is larger than the sum of its proper divisors (12511927).

21011913 is a wasteful number, since it uses less digits than its factorization.

21011913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59885 (or 59879 counting only the distinct ones).

The product of its (nonzero) digits is 54, while the sum is 18.

The square root of 21011913 is about 4583.8753255297. The cubic root of 21011913 is about 275.9445777185.

Adding to 21011913 its reverse (31911012), we get a palindrome (52922925).

The spelling of 21011913 in words is "twenty-one million, eleven thousand, nine hundred thirteen".