667156621 has 2 divisors, whose sum is σ = 667156622. Its totient is φ = 667156620.

The previous prime is 667156603. The next prime is 667156631. The reversal of 667156621 is 126651766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 402443721 + 264712900 = 20061^2 + 16270^2 .

It is a cyclic number.

It is not a de Polignac number, because 667156621 - 2¹³ = 667148429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (667156631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333578310 + 333578311.

It is an arithmetic number, because the mean of its divisors is an integer number (333578311).

Almost surely, 2^667156621 is an apocalyptic number.

It is an amenable number.

667156621 is a deficient number, since it is larger than the sum of its proper divisors (1).

667156621 is an equidigital number, since it uses as much as digits as its factorization.

667156621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 40.

The square root of 667156621 is about 25829.3751569797. The cubic root of 667156621 is about 873.7944195979.

The spelling of 667156621 in words is "six hundred sixty-seven million, one hundred fifty-six thousand, six hundred twenty-one".