129201661 has 4 divisors (see below), whose sum is σ = 131130112. Its totient is φ = 127273212.

The previous prime is 129201659. The next prime is 129201671. The reversal of 129201661 is 166102921.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 166102921 = 19 ⋅8742259.

It is a cyclic number.

It is not a de Polignac number, because 129201661 - 2¹ = 129201659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129201671) 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, 964125 + ... + 964258.

It is an arithmetic number, because the mean of its divisors is an integer number (32782528).

Almost surely, 2^129201661 is an apocalyptic number.

It is an amenable number.

129201661 is a deficient number, since it is larger than the sum of its proper divisors (1928451).

129201661 is an equidigital number, since it uses as much as digits as its factorization.

129201661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1928450.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 129201661 is about 11366.6908553017. The cubic root of 129201661 is about 505.5405915754.

The spelling of 129201661 in words is "one hundred twenty-nine million, two hundred one thousand, six hundred sixty-one".