129721808 has 10 divisors (see below), whose sum is σ = 251336034. Its totient is φ = 64860896.

The previous prime is 129721783. The next prime is 129721811. The reversal of 129721808 is 808127921.

It can be written as a sum of positive squares in only one way, i.e., 129322384 + 399424 = 11372^2 + 632^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4053791 + ... + 4053822.

Almost surely, 2^129721808 is an apocalyptic number.

It is an amenable number.

129721808 is a deficient number, since it is larger than the sum of its proper divisors (121614226).

129721808 is an equidigital number, since it uses as much as digits as its factorization.

129721808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8107621 (or 8107615 counting only the distinct ones).

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

The square root of 129721808 is about 11389.5481912146. The cubic root of 129721808 is about 506.2180940518.

The spelling of 129721808 in words is "one hundred twenty-nine million, seven hundred twenty-one thousand, eight hundred eight".