16640621 has 2 divisors, whose sum is σ = 16640622. Its totient is φ = 16640620.

The previous prime is 16640593. The next prime is 16640647. The reversal of 16640621 is 12604661.

It is a happy number.

It is an a-pointer prime, because the next prime (16640647) can be obtained adding 16640621 to its sum of digits (26).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11464996 + 5175625 = 3386^2 + 2275^2 .

It is an emirp because it is prime and its reverse (12604661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16640621 - 2¹⁸ = 16378477 is a prime.

It is a Chen prime.

It is equal to p_1069631 and since 16640621 and 1069631 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16640651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8320310 + 8320311.

It is an arithmetic number, because the mean of its divisors is an integer number (8320311).

Almost surely, 2^16640621 is an apocalyptic number.

It is an amenable number.

16640621 is a deficient number, since it is larger than the sum of its proper divisors (1).

16640621 is an equidigital number, since it uses as much as digits as its factorization.

16640621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 16640621 is about 4079.2917277390. The cubic root of 16640621 is about 255.3033478245.

The spelling of 16640621 in words is "sixteen million, six hundred forty thousand, six hundred twenty-one".