133817687721 has 9 divisors (see below), whose sum is σ = 193293800791. Its totient is φ = 89211060192.

The previous prime is 133817687719. The next prime is 133817687723. The reversal of 133817687721 is 127786718331.

The square root of 133817687721 is 365811.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (133817687719) and next prime (133817687723).

It can be written as a sum of positive squares in only one way, i.e., 18310149225 + 115507538496 = 135315^2 + 339864^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 133817687721 - 2¹ = 133817687719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (133817687723) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1036465 + ... + 1158401.

Almost surely, 2^133817687721 is an apocalyptic number.

133817687721 is the 365811-st square number.

133817687721 is the 182906-th centered octagonal number.

It is an amenable number.

133817687721 is a deficient number, since it is larger than the sum of its proper divisors (59476113070).

133817687721 is an frugal number, since it uses more digits than its factorization.

133817687721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243880 (or 121940 counting only the distinct ones).

The product of its digits is 2370816, while the sum is 54.

The spelling of 133817687721 in words is "one hundred thirty-three billion, eight hundred seventeen million, six hundred eighty-seven thousand, seven hundred twenty-one".