21001312331 has 4 divisors (see below), whose sum is σ = 21028623000. Its totient is φ = 20974001664.

The previous prime is 21001312327. The next prime is 21001312333. The reversal of 21001312331 is 13321310012.

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 21001312331 - 2² = 21001312327 is a prime.

It is a super-2 number, since 2×21001312331² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001312333) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13654181 + ... + 13655718.

It is an arithmetic number, because the mean of its divisors is an integer number (5257155750).

Almost surely, 2^21001312331 is an apocalyptic number.

21001312331 is a deficient number, since it is larger than the sum of its proper divisors (27310669).

21001312331 is an equidigital number, since it uses as much as digits as its factorization.

21001312331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27310668.

The product of its (nonzero) digits is 108, while the sum is 17.

Adding to 21001312331 its reverse (13321310012), we get a palindrome (34322622343).

The spelling of 21001312331 in words is "twenty-one billion, one million, three hundred twelve thousand, three hundred thirty-one".