21001012031 has 4 divisors (see below), whose sum is σ = 21678464064. Its totient is φ = 20323560000.

The previous prime is 21001012007. The next prime is 21001012049. The reversal of 21001012031 is 13021010012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001012031 is a prime.

It is a super-2 number, since 2×21001012031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001012051) 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, 338725970 + ... + 338726031.

It is an arithmetic number, because the mean of its divisors is an integer number (5419616016).

Almost surely, 2^21001012031 is an apocalyptic number.

21001012031 is a deficient number, since it is larger than the sum of its proper divisors (677452033).

21001012031 is an equidigital number, since it uses as much as digits as its factorization.

21001012031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 677452032.

The product of its (nonzero) digits is 12, while the sum is 11.

Adding to 21001012031 its reverse (13021010012), we get a palindrome (34022022043).

The spelling of 21001012031 in words is "twenty-one billion, one million, twelve thousand, thirty-one".