321665621 has 2 divisors, whose sum is σ = 321665622. Its totient is φ = 321665620.

The previous prime is 321665609. The next prime is 321665629. The reversal of 321665621 is 126566123.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 215678596 + 105987025 = 14686^2 + 10295^2 .

It is an emirp because it is prime and its reverse (126566123) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 321665621 - 2¹⁰ = 321664597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (321665629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160832810 + 160832811.

It is an arithmetic number, because the mean of its divisors is an integer number (160832811).

Almost surely, 2^321665621 is an apocalyptic number.

It is an amenable number.

321665621 is a deficient number, since it is larger than the sum of its proper divisors (1).

321665621 is an equidigital number, since it uses as much as digits as its factorization.

321665621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 32.

The square root of 321665621 is about 17935.0389182739. The cubic root of 321665621 is about 685.1750638566.

The spelling of 321665621 in words is "three hundred twenty-one million, six hundred sixty-five thousand, six hundred twenty-one".