133661921 has 2 divisors, whose sum is σ = 133661922. Its totient is φ = 133661920.

The previous prime is 133661911. The next prime is 133661923. The reversal of 133661921 is 129166331.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 129504400 + 4157521 = 11380^2 + 2039^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-133661921 is a prime.

Together with 133661923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (133661923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 66830960 + 66830961.

It is an arithmetic number, because the mean of its divisors is an integer number (66830961).

Almost surely, 2^133661921 is an apocalyptic number.

It is an amenable number.

133661921 is a deficient number, since it is larger than the sum of its proper divisors (1).

133661921 is an equidigital number, since it uses as much as digits as its factorization.

133661921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832, while the sum is 32.

The square root of 133661921 is about 11561.2248918529. The cubic root of 133661921 is about 511.2922770378.

The spelling of 133661921 in words is "one hundred thirty-three million, six hundred sixty-one thousand, nine hundred twenty-one".