221991247 has 2 divisors, whose sum is σ = 221991248. Its totient is φ = 221991246.

The previous prime is 221991221. The next prime is 221991277. The reversal of 221991247 is 742199122.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221991247 is a prime.

It is a super-2 number, since 2×221991247² = 98560227489230018, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221991277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110995623 + 110995624.

It is an arithmetic number, because the mean of its divisors is an integer number (110995624).

Almost surely, 2^221991247 is an apocalyptic number.

221991247 is a deficient number, since it is larger than the sum of its proper divisors (1).

221991247 is an equidigital number, since it uses as much as digits as its factorization.

221991247 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 221991247 is about 14899.3706914084. The cubic root of 221991247 is about 605.4969366121.

The spelling of 221991247 in words is "two hundred twenty-one million, nine hundred ninety-one thousand, two hundred forty-seven".