221971957 has 2 divisors, whose sum is σ = 221971958. Its totient is φ = 221971956.

The previous prime is 221971943. The next prime is 221971969. The reversal of 221971957 is 759179122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 174002481 + 47969476 = 13191^2 + 6926^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221971957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221941957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110985978 + 110985979.

It is an arithmetic number, because the mean of its divisors is an integer number (110985979).

Almost surely, 2^221971957 is an apocalyptic number.

It is an amenable number.

221971957 is a deficient number, since it is larger than the sum of its proper divisors (1).

221971957 is an equidigital number, since it uses as much as digits as its factorization.

221971957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 79380, while the sum is 43.

The square root of 221971957 is about 14898.7233345680. The cubic root of 221971957 is about 605.4793978211.

The spelling of 221971957 in words is "two hundred twenty-one million, nine hundred seventy-one thousand, nine hundred fifty-seven".