221978696021 has 2 divisors, whose sum is σ = 221978696022. Its totient is φ = 221978696020.

The previous prime is 221978695993. The next prime is 221978696039. The reversal of 221978696021 is 120696879122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 217239888100 + 4738807921 = 466090^2 + 68839^2 .

It is a cyclic number.

It is not a de Polignac number, because 221978696021 - 2⁶ = 221978695957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221978696081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110989348010 + 110989348011.

It is an arithmetic number, because the mean of its divisors is an integer number (110989348011).

Almost surely, 2^221978696021 is an apocalyptic number.

It is an amenable number.

221978696021 is a deficient number, since it is larger than the sum of its proper divisors (1).

221978696021 is an equidigital number, since it uses as much as digits as its factorization.

221978696021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1306368, while the sum is 53.

The spelling of 221978696021 in words is "two hundred twenty-one billion, nine hundred seventy-eight million, six hundred ninety-six thousand, twenty-one".