21311213 has 16 divisors (see below), whose sum is σ = 27025920. Its totient is φ = 16321200.

The previous prime is 21311177. The next prime is 21311219. The reversal of 21311213 is 31211312.

It is not a de Polignac number, because 21311213 - 2⁸ = 21310957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311219) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2198 + ... + 6888.

It is an arithmetic number, because the mean of its divisors is an integer number (1689120).

Almost surely, 2^21311213 is an apocalyptic number.

It is an amenable number.

21311213 is a deficient number, since it is larger than the sum of its proper divisors (5714707).

21311213 is a wasteful number, since it uses less digits than its factorization.

21311213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4768.

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

The square root of 21311213 is about 4616.4069361355. The cubic root of 21311213 is about 277.2486179488.

Adding to 21311213 its reverse (31211312), we get a palindrome (52522525).

Subtracting 21311213 from its reverse (31211312), we obtain a palindrome (9900099).

The spelling of 21311213 in words is "twenty-one million, three hundred eleven thousand, two hundred thirteen".