1210000021 has 2 divisors, whose sum is σ = 1210000022. Its totient is φ = 1210000020.

The previous prime is 1210000013. The next prime is 1210000037. The reversal of 1210000021 is 1200000121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 742835025 + 467164996 = 27255^2 + 21614^2 .

It is an emirp because it is prime and its reverse (1200000121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1210000021 - 2³ = 1210000013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1209999959 and 1210000013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1210000081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605000010 + 605000011.

It is an arithmetic number, because the mean of its divisors is an integer number (605000011).

Almost surely, 2^1210000021 is an apocalyptic number.

It is an amenable number.

1210000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1210000021 is an equidigital number, since it uses as much as digits as its factorization.

1210000021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 1210000021 is about 34785.0545637059. The cubic root of 1210000021 is about 1065.6022429313.

Adding to 1210000021 its reverse (1200000121), we get a palindrome (2410000142).

The spelling of 1210000021 in words is "one billion, two hundred ten million, twenty-one", and thus it is an aban number.