21000121031 has 2 divisors, whose sum is σ = 21000121032. Its totient is φ = 21000121030.

The previous prime is 21000120971. The next prime is 21000121039. The reversal of 21000121031 is 13012100012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000121031 is a prime.

It is a super-2 number, since 2×21000121031² (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 (21000121039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500060515 + 10500060516.

It is an arithmetic number, because the mean of its divisors is an integer number (10500060516).

Almost surely, 2^21000121031 is an apocalyptic number.

21000121031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000121031 is an equidigital number, since it uses as much as digits as its factorization.

21000121031 is an odious number, because the sum of its binary digits is odd.

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

Adding to 21000121031 its reverse (13012100012), we get a palindrome (34012221043).

The spelling of 21000121031 in words is "twenty-one billion, one hundred twenty-one thousand, thirty-one".