634221781 has 2 divisors, whose sum is σ = 634221782. Its totient is φ = 634221780.

The previous prime is 634221769. The next prime is 634221787. The reversal of 634221781 is 187122436.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 628504900 + 5716881 = 25070^2 + 2391^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-634221781 is a prime.

It is a super-2 number, since 2×634221781² = 804474534989623922, which contains 22 as substring.

It is a zygodrome in base 5.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (634221787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 317110890 + 317110891.

It is an arithmetic number, because the mean of its divisors is an integer number (317110891).

Almost surely, 2^634221781 is an apocalyptic number.

It is an amenable number.

634221781 is a deficient number, since it is larger than the sum of its proper divisors (1).

634221781 is an equidigital number, since it uses as much as digits as its factorization.

634221781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16128, while the sum is 34.

The square root of 634221781 is about 25183.7602633125. The cubic root of 634221781 is about 859.1725324653.

The spelling of 634221781 in words is "six hundred thirty-four million, two hundred twenty-one thousand, seven hundred eighty-one".