263251981 has 2 divisors, whose sum is σ = 263251982. Its totient is φ = 263251980.

The previous prime is 263251979. The next prime is 263252069. The reversal of 263251981 is 189152362.

263251981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 158004900 + 105247081 = 12570^2 + 10259^2 .

It is a cyclic number.

It is not a de Polignac number, because 263251981 - 2¹ = 263251979 is a prime.

It is a super-2 number, since 2×263251981² = 138603211000848722, which contains 22 as substring.

Together with 263251979, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 263251981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (263251921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 131625990 + 131625991.

It is an arithmetic number, because the mean of its divisors is an integer number (131625991).

Almost surely, 2^263251981 is an apocalyptic number.

It is an amenable number.

263251981 is a deficient number, since it is larger than the sum of its proper divisors (1).

263251981 is an equidigital number, since it uses as much as digits as its factorization.

263251981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 37.

The square root of 263251981 is about 16225.0417873114. The cubic root of 263251981 is about 640.9004098740.

The spelling of 263251981 in words is "two hundred sixty-three million, two hundred fifty-one thousand, nine hundred eighty-one".