661621423 has 2 divisors, whose sum is σ = 661621424. Its totient is φ = 661621422.

The previous prime is 661621403. The next prime is 661621447. The reversal of 661621423 is 324126166.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661621423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661621403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330810711 + 330810712.

It is an arithmetic number, because the mean of its divisors is an integer number (330810712).

Almost surely, 2^661621423 is an apocalyptic number.

661621423 is a deficient number, since it is larger than the sum of its proper divisors (1).

661621423 is an equidigital number, since it uses as much as digits as its factorization.

661621423 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 31.

The square root of 661621423 is about 25722.0027019670. The cubic root of 661621423 is about 871.3711689566.

Adding to 661621423 its reverse (324126166), we get a palindrome (985747589).

The spelling of 661621423 in words is "six hundred sixty-one million, six hundred twenty-one thousand, four hundred twenty-three".