181621001 has 2 divisors, whose sum is σ = 181621002. Its totient is φ = 181621000.

The previous prime is 181620977. The next prime is 181621003. The reversal of 181621001 is 100126181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 96040000 + 85581001 = 9800^2 + 9251^2 .

It is a cyclic number.

It is not a de Polignac number, because 181621001 - 2¹⁴ = 181604617 is a prime.

Together with 181621003, 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 (181621003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90810500 + 90810501.

It is an arithmetic number, because the mean of its divisors is an integer number (90810501).

Almost surely, 2^181621001 is an apocalyptic number.

It is an amenable number.

181621001 is a deficient number, since it is larger than the sum of its proper divisors (1).

181621001 is an equidigital number, since it uses as much as digits as its factorization.

181621001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 20.

The square root of 181621001 is about 13476.6836053979. The cubic root of 181621001 is about 566.3114662487.

Adding to 181621001 its reverse (100126181), we get a palindrome (281747182).

The spelling of 181621001 in words is "one hundred eighty-one million, six hundred twenty-one thousand, one".