20129665 has 16 divisors (see below), whose sum is σ = 25288848. Its totient is φ = 15365376.

The previous prime is 20129663. The next prime is 20129671. The reversal of 20129665 is 56692102.

It can be written as a sum of positive squares in 8 ways, for example, as 1527696 + 18601969 = 1236^2 + 4313^2 .

It is a cyclic number.

It is not a de Polignac number, because 20129665 - 2¹ = 20129663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20129663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8779 + ... + 10831.

It is an arithmetic number, because the mean of its divisors is an integer number (1580553).

Almost surely, 2^20129665 is an apocalyptic number.

It is an amenable number.

20129665 is a deficient number, since it is larger than the sum of its proper divisors (5159183).

20129665 is a wasteful number, since it uses less digits than its factorization.

20129665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2148.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 20129665 is about 4486.6095216767. The cubic root of 20129665 is about 272.0271067636.

The spelling of 20129665 in words is "twenty million, one hundred twenty-nine thousand, six hundred sixty-five".