129777665 has 4 divisors (see below), whose sum is σ = 155733204. Its totient is φ = 103822128.

The previous prime is 129777649. The next prime is 129777667. The reversal of 129777665 is 566777921.

It is a Cunningham number, because it is equal to 11392²+1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 46730896 + 83046769 = 6836^2 + 9113^2 .

It is a cyclic number.

It is not a de Polignac number, because 129777665 - 2⁴ = 129777649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129777667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12977762 + ... + 12977771.

It is an arithmetic number, because the mean of its divisors is an integer number (38933301).

It is a Proth number, since it is equal to 7921 ⋅ 2¹⁴ + 1 and 7921 < 2¹⁴.

Almost surely, 2^129777665 is an apocalyptic number.

It is an amenable number.

129777665 is a deficient number, since it is larger than the sum of its proper divisors (25955539).

129777665 is an equidigital number, since it uses as much as digits as its factorization.

129777665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25955538.

The product of its digits is 1111320, while the sum is 50.

The square root of 129777665 is about 11392.0000438904. Note that the first 4 decimals coincide. The cubic root of 129777665 is about 506.2907412215.

The spelling of 129777665 in words is "one hundred twenty-nine million, seven hundred seventy-seven thousand, six hundred sixty-five".