21000021061 has 2 divisors, whose sum is σ = 21000021062. Its totient is φ = 21000021060.

The previous prime is 21000021059. The next prime is 21000021113. The reversal of 21000021061 is 16012000012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19354096161 + 1645924900 = 139119^2 + 40570^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000021061 - 2¹ = 21000021059 is a prime.

Together with 21000021059, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000021761) 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 as a sum of consecutive naturals, namely, 10500010530 + 10500010531.

It is an arithmetic number, because the mean of its divisors is an integer number (10500010531).

Almost surely, 2^21000021061 is an apocalyptic number.

It is an amenable number.

21000021061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000021061 is an equidigital number, since it uses as much as digits as its factorization.

21000021061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 21000021061 its reverse (16012000012), we get a palindrome (37012021073).

The spelling of 21000021061 in words is "twenty-one billion, twenty-one thousand, sixty-one".