209920481 has 2 divisors, whose sum is σ = 209920482. Its totient is φ = 209920480.

The previous prime is 209920463. The next prime is 209920483. The reversal of 209920481 is 184029902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 146797456 + 63123025 = 12116^2 + 7945^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209920481 is a prime.

It is a super-2 number, since 2×209920481² = 88133216686542722, which contains 22 as substring.

Together with 209920483, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (209920483) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104960240 + 104960241.

It is an arithmetic number, because the mean of its divisors is an integer number (104960241).

Almost surely, 2^209920481 is an apocalyptic number.

209920481 is the 7745-th centered heptagonal number.

It is an amenable number.

209920481 is a deficient number, since it is larger than the sum of its proper divisors (1).

209920481 is an equidigital number, since it uses as much as digits as its factorization.

209920481 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 209920481 is about 14488.6328202491. The cubic root of 209920481 is about 594.3171612444.

The spelling of 209920481 in words is "two hundred nine million, nine hundred twenty thousand, four hundred eighty-one".