551997661 has 2 divisors, whose sum is σ = 551997662. Its totient is φ = 551997660.

The previous prime is 551997659. The next prime is 551997673. The reversal of 551997661 is 166799155.

551997661 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., 342472036 + 209525625 = 18506^2 + 14475^2 .

It is a cyclic number.

It is not a de Polignac number, because 551997661 - 2¹ = 551997659 is a prime.

Together with 551997659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (551997161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 275998830 + 275998831.

It is an arithmetic number, because the mean of its divisors is an integer number (275998831).

Almost surely, 2^551997661 is an apocalyptic number.

It is an amenable number.

551997661 is a deficient number, since it is larger than the sum of its proper divisors (1).

551997661 is an equidigital number, since it uses as much as digits as its factorization.

551997661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 510300, while the sum is 49.

The square root of 551997661 is about 23494.6304716631. The cubic root of 551997661 is about 820.3120272960.

The spelling of 551997661 in words is "five hundred fifty-one million, nine hundred ninety-seven thousand, six hundred sixty-one".