220691981 has 2 divisors, whose sum is σ = 220691982. Its totient is φ = 220691980.

The previous prime is 220691959. The next prime is 220691983. The reversal of 220691981 is 189196022.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 152893225 + 67798756 = 12365^2 + 8234^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-220691981 is a prime.

It is a super-2 number, since 2×220691981² = 97409900955408722, which contains 22 as substring.

Together with 220691983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (220691983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110345990 + 110345991.

It is an arithmetic number, because the mean of its divisors is an integer number (110345991).

Almost surely, 2^220691981 is an apocalyptic number.

It is an amenable number.

220691981 is a deficient number, since it is larger than the sum of its proper divisors (1).

220691981 is an equidigital number, since it uses as much as digits as its factorization.

220691981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 220691981 is about 14855.7053349883. The cubic root of 220691981 is about 604.3133443148.

The spelling of 220691981 in words is "two hundred twenty million, six hundred ninety-one thousand, nine hundred eighty-one".