661633601 has 2 divisors, whose sum is σ = 661633602. Its totient is φ = 661633600.

The previous prime is 661633573. The next prime is 661633603. The reversal of 661633601 is 106336166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 397603600 + 264030001 = 19940^2 + 16249^2 .

It is a cyclic number.

It is not a de Polignac number, because 661633601 - 2¹⁴ = 661617217 is a prime.

It is a Sophie Germain prime.

Together with 661633603, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (661633603) 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, 330816800 + 330816801.

It is an arithmetic number, because the mean of its divisors is an integer number (330816801).

Almost surely, 2^661633601 is an apocalyptic number.

It is an amenable number.

661633601 is a deficient number, since it is larger than the sum of its proper divisors (1).

661633601 is an equidigital number, since it uses as much as digits as its factorization.

661633601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11664, while the sum is 32.

The square root of 661633601 is about 25722.2394242803. The cubic root of 661633601 is about 871.3765151625.

Adding to 661633601 its reverse (106336166), we get a palindrome (767969767).

The spelling of 661633601 in words is "six hundred sixty-one million, six hundred thirty-three thousand, six hundred one".