647663881 has 2 divisors, whose sum is σ = 647663882. Its totient is φ = 647663880.

The previous prime is 647663851. The next prime is 647663899. The reversal of 647663881 is 188366746.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 519612025 + 128051856 = 22795^2 + 11316^2 .

It is a cyclic number.

It is not a de Polignac number, because 647663881 - 2⁹ = 647663369 is a prime.

It is a super-2 number, since 2×647663881² = 838937005503964322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (647663851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323831940 + 323831941.

It is an arithmetic number, because the mean of its divisors is an integer number (323831941).

Almost surely, 2^647663881 is an apocalyptic number.

It is an amenable number.

647663881 is a deficient number, since it is larger than the sum of its proper divisors (1).

647663881 is an equidigital number, since it uses as much as digits as its factorization.

647663881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1161216, while the sum is 49.

The square root of 647663881 is about 25449.2412657038. The cubic root of 647663881 is about 865.2000967140.

The spelling of 647663881 in words is "six hundred forty-seven million, six hundred sixty-three thousand, eight hundred eighty-one".