661623379 has 2 divisors, whose sum is σ = 661623380. Its totient is φ = 661623378.

The previous prime is 661623353. The next prime is 661623407. The reversal of 661623379 is 973326166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661623379 - 2⁷ = 661623251 is a prime.

It is not a weakly prime, because it can be changed into another prime (661623329) 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, 330811689 + 330811690.

It is an arithmetic number, because the mean of its divisors is an integer number (330811690).

Almost surely, 2^661623379 is an apocalyptic number.

661623379 is a deficient number, since it is larger than the sum of its proper divisors (1).

661623379 is an equidigital number, since it uses as much as digits as its factorization.

661623379 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 244944, while the sum is 43.

The square root of 661623379 is about 25722.0407238617. The cubic root of 661623379 is about 871.3720276553.

The spelling of 661623379 in words is "six hundred sixty-one million, six hundred twenty-three thousand, three hundred seventy-nine".