21311220311 has 4 divisors (see below), whose sum is σ = 21312720072. Its totient is φ = 21309720552.

The previous prime is 21311220263. The next prime is 21311220317. The reversal of 21311220311 is 11302211312.

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

It is a cyclic number.

It is not a de Polignac number, because 21311220311 - 2¹⁰ = 21311219287 is a prime.

It is a super-2 number, since 2×21311220311² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21311220311.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311220317) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 728360 + ... + 757053.

It is an arithmetic number, because the mean of its divisors is an integer number (5328180018).

Almost surely, 2^21311220311 is an apocalyptic number.

21311220311 is a deficient number, since it is larger than the sum of its proper divisors (1499761).

21311220311 is a wasteful number, since it uses less digits than its factorization.

21311220311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1499760.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21311220311 its reverse (11302211312), we get a palindrome (32613431623).

The spelling of 21311220311 in words is "twenty-one billion, three hundred eleven million, two hundred twenty thousand, three hundred eleven".