129878021 has 24 divisors (see below), whose sum is σ = 162468864. Its totient is φ = 101649600.

The previous prime is 129878009. The next prime is 129878027. The reversal of 129878021 is 120878921.

It is not a de Polignac number, because 129878021 - 2¹⁰ = 129876997 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 (129878027) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 118940 + ... + 120026.

It is an arithmetic number, because the mean of its divisors is an integer number (6769536).

Almost surely, 2^129878021 is an apocalyptic number.

It is an amenable number.

129878021 is a deficient number, since it is larger than the sum of its proper divisors (32590843).

129878021 is a wasteful number, since it uses less digits than its factorization.

129878021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1221 (or 1208 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 38.

The square root of 129878021 is about 11396.4038626226. The cubic root of 129878021 is about 506.4212110843.

The spelling of 129878021 in words is "one hundred twenty-nine million, eight hundred seventy-eight thousand, twenty-one".