21047436121 has 2 divisors, whose sum is σ = 21047436122. Its totient is φ = 21047436120.

The previous prime is 21047436107. The next prime is 21047436203. The reversal of 21047436121 is 12163474012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19617083721 + 1430352400 = 140061^2 + 37820^2 .

It is a cyclic number.

It is not a de Polignac number, because 21047436121 - 2⁹ = 21047435609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21047437121) 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, 10523718060 + 10523718061.

It is an arithmetic number, because the mean of its divisors is an integer number (10523718061).

Almost surely, 2^21047436121 is an apocalyptic number.

It is an amenable number.

21047436121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21047436121 is an equidigital number, since it uses as much as digits as its factorization.

21047436121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 31.

The spelling of 21047436121 in words is "twenty-one billion, forty-seven million, four hundred thirty-six thousand, one hundred twenty-one".