133656721 has 9 divisors (see below), whose sum is σ = 147051849. Its totient is φ = 121390500.

The previous prime is 133656709. The next prime is 133656727. The reversal of 133656721 is 127656331.

The square root of 133656721 is 11561.

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

It is not a de Polignac number, because 133656721 - 2⁵ = 133656689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (133656727) 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, 126646 + ... + 127696.

Almost surely, 2^133656721 is an apocalyptic number.

133656721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

133656721 is the 11561-st square number.

133656721 is the 5781-st centered octagonal number.

It is an amenable number.

133656721 is a deficient number, since it is larger than the sum of its proper divisors (13395128).

133656721 is an frugal number, since it uses more digits than its factorization.

133656721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2124 (or 1062 counting only the distinct ones).

The product of its digits is 22680, while the sum is 34.

The cubic root of 133656721 is about 511.2856464924.

The spelling of 133656721 in words is "one hundred thirty-three million, six hundred fifty-six thousand, seven hundred twenty-one".