21000004031 has 2 divisors, whose sum is σ = 21000004032. Its totient is φ = 21000004030.

The previous prime is 21000004013. The next prime is 21000004043. The reversal of 21000004031 is 13040000012.

It is a happy number.

Together with previous prime (21000004013) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000004031 is a prime.

It is a super-2 number, since 2×21000004031² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000004331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500002015 + 10500002016.

It is an arithmetic number, because the mean of its divisors is an integer number (10500002016).

Almost surely, 2^21000004031 is an apocalyptic number.

21000004031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000004031 is an equidigital number, since it uses as much as digits as its factorization.

21000004031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 11.

Adding to 21000004031 its reverse (13040000012), we get a palindrome (34040004043).

The spelling of 21000004031 in words is "twenty-one billion, four thousand, thirty-one".