129021981 has 32 divisors (see below), whose sum is σ = 194088960. Its totient is φ = 75566400.

The previous prime is 129021979. The next prime is 129022009. The reversal of 129021981 is 189120921.

It is not a de Polignac number, because 129021981 - 2¹ = 129021979 is a prime.

It is a super-3 number, since 3×129021981³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129021901) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 123660 + ... + 124698.

It is an arithmetic number, because the mean of its divisors is an integer number (6065280).

Almost surely, 2^129021981 is an apocalyptic number.

129021981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

129021981 is a deficient number, since it is larger than the sum of its proper divisors (65066979).

129021981 is a wasteful number, since it uses less digits than its factorization.

129021981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1177.

The product of its (nonzero) digits is 2592, while the sum is 33.

The square root of 129021981 is about 11358.7843099515. The cubic root of 129021981 is about 505.3061320659.

The spelling of 129021981 in words is "one hundred twenty-nine million, twenty-one thousand, nine hundred eighty-one".