21011220947 has 2 divisors, whose sum is σ = 21011220948. Its totient is φ = 21011220946.

The previous prime is 21011220917. The next prime is 21011220953. The reversal of 21011220947 is 74902211012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21011220947 - 2⁶ = 21011220883 is a prime.

It is not a weakly prime, because it can be changed into another prime (21011220917) 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, 10505610473 + 10505610474.

It is an arithmetic number, because the mean of its divisors is an integer number (10505610474).

Almost surely, 2^21011220947 is an apocalyptic number.

21011220947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011220947 is an equidigital number, since it uses as much as digits as its factorization.

21011220947 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 29.

Adding to 21011220947 its reverse (74902211012), we get a palindrome (95913431959).

The spelling of 21011220947 in words is "twenty-one billion, eleven million, two hundred twenty thousand, nine hundred forty-seven".