129720917 has 4 divisors (see below), whose sum is σ = 129761376. Its totient is φ = 129680460.

The previous prime is 129720907. The next prime is 129720919. The reversal of 129720917 is 719027921.

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: 719027921 = 83 ⋅8662987.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-129720917 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 (129720919) 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, 14963 + ... + 21984.

It is an arithmetic number, because the mean of its divisors is an integer number (32440344).

Almost surely, 2^129720917 is an apocalyptic number.

It is an amenable number.

129720917 is a deficient number, since it is larger than the sum of its proper divisors (40459).

129720917 is an equidigital number, since it uses as much as digits as its factorization.

129720917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40458.

The product of its (nonzero) digits is 15876, while the sum is 38.

The square root of 129720917 is about 11389.5090763386. The cubic root of 129720917 is about 506.2169350553.

The spelling of 129720917 in words is "one hundred twenty-nine million, seven hundred twenty thousand, nine hundred seventeen".