21012997 has 2 divisors, whose sum is σ = 21012998. Its totient is φ = 21012996.

The previous prime is 21012991. The next prime is 21013019. The reversal of 21012997 is 79921012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13905441 + 7107556 = 3729^2 + 2666^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012997 - 2²³ = 12624389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506498 + 10506499.

It is an arithmetic number, because the mean of its divisors is an integer number (10506499).

Almost surely, 2^21012997 is an apocalyptic number.

It is an amenable number.

21012997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012997 is an equidigital number, since it uses as much as digits as its factorization.

21012997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21012997 is about 4583.9935645679. The cubic root of 21012997 is about 275.9493229438.

The spelling of 21012997 in words is "twenty-one million, twelve thousand, nine hundred ninety-seven".