505921781 has 2 divisors, whose sum is σ = 505921782. Its totient is φ = 505921780.

The previous prime is 505921763. The next prime is 505921783. The reversal of 505921781 is 187129505.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 449821681 + 56100100 = 21209^2 + 7490^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-505921781 is a prime.

It is a super-2 number, since 2×505921781² = 511913696980423922, which contains 22 as substring.

Together with 505921783, 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 (505921783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 252960890 + 252960891.

It is an arithmetic number, because the mean of its divisors is an integer number (252960891).

Almost surely, 2^505921781 is an apocalyptic number.

It is an amenable number.

505921781 is a deficient number, since it is larger than the sum of its proper divisors (1).

505921781 is an equidigital number, since it uses as much as digits as its factorization.

505921781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25200, while the sum is 38.

The square root of 505921781 is about 22492.7050618639. The cubic root of 505921781 is about 796.8216502764.

The spelling of 505921781 in words is "five hundred five million, nine hundred twenty-one thousand, seven hundred eighty-one".