21221999947 has 2 divisors, whose sum is σ = 21221999948. Its totient is φ = 21221999946.

The previous prime is 21221999941. The next prime is 21221999993. The reversal of 21221999947 is 74999912212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21221999947 - 2⁷ = 21221999819 is a prime.

It is not a weakly prime, because it can be changed into another prime (21221999941) 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, 10610999973 + 10610999974.

It is an arithmetic number, because the mean of its divisors is an integer number (10610999974).

Almost surely, 2^21221999947 is an apocalyptic number.

21221999947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221999947 is an equidigital number, since it uses as much as digits as its factorization.

21221999947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1469664, while the sum is 55.

The spelling of 21221999947 in words is "twenty-one billion, two hundred twenty-one million, nine hundred ninety-nine thousand, nine hundred forty-seven".