21212121947 has 2 divisors, whose sum is σ = 21212121948. Its totient is φ = 21212121946.

The previous prime is 21212121937. The next prime is 21212121971. The reversal of 21212121947 is 74912121212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21212121947 - 2⁸ = 21212121691 is a prime.

It is not a weakly prime, because it can be changed into another prime (21212121937) 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, 10606060973 + 10606060974.

It is an arithmetic number, because the mean of its divisors is an integer number (10606060974).

Almost surely, 2^21212121947 is an apocalyptic number.

21212121947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212121947 is an equidigital number, since it uses as much as digits as its factorization.

21212121947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 32.

The spelling of 21212121947 in words is "twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, nine hundred forty-seven".