21311321533 has 8 divisors (see below), whose sum is σ = 22643013240. Its totient is φ = 20057709760.

The previous prime is 21311321527. The next prime is 21311321543. The reversal of 21311321533 is 33512311312.

It can be written as a sum of positive squares in 4 ways, for example, as 6958562724 + 14352758809 = 83418^2 + 119803^2 .

It is not a de Polignac number, because 21311321533 - 2¹³ = 21311313341 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311321498 and 21311321507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311321543) 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, 2163958 + ... + 2173783.

It is an arithmetic number, because the mean of its divisors is an integer number (2830376655).

Almost surely, 2^21311321533 is an apocalyptic number.

It is an amenable number.

21311321533 is a deficient number, since it is larger than the sum of its proper divisors (1331691707).

21311321533 is an frugal number, since it uses more digits than its factorization.

21311321533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4337792 (or 4337758 counting only the distinct ones).

The product of its digits is 1620, while the sum is 25.

Adding to 21311321533 its reverse (33512311312), we get a palindrome (54823632845).

The spelling of 21311321533 in words is "twenty-one billion, three hundred eleven million, three hundred twenty-one thousand, five hundred thirty-three".