661929109 has 2 divisors, whose sum is σ = 661929110. Its totient is φ = 661929108.

The previous prime is 661929097. The next prime is 661929131. The reversal of 661929109 is 901929166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 419348484 + 242580625 = 20478^2 + 15575^2 .

It is a cyclic number.

It is not a de Polignac number, because 661929109 - 2¹⁵ = 661896341 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661929139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330964554 + 330964555.

It is an arithmetic number, because the mean of its divisors is an integer number (330964555).

Almost surely, 2^661929109 is an apocalyptic number.

It is an amenable number.

661929109 is a deficient number, since it is larger than the sum of its proper divisors (1).

661929109 is an equidigital number, since it uses as much as digits as its factorization.

661929109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 52488, while the sum is 43.

The square root of 661929109 is about 25727.9829951747. The cubic root of 661929109 is about 871.5062246192.

The spelling of 661929109 in words is "six hundred sixty-one million, nine hundred twenty-nine thousand, one hundred nine".