16646207621 has 2 divisors, whose sum is σ = 16646207622. Its totient is φ = 16646207620.

The previous prime is 16646207581. The next prime is 16646207639. The reversal of 16646207621 is 12670264661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12929964100 + 3716243521 = 113710^2 + 60961^2 .

It is an emirp because it is prime and its reverse (12670264661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16646207621 - 2¹⁰ = 16646206597 is a prime.

It is a super-2 number, since 2×16646207621² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16646207651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8323103810 + 8323103811.

It is an arithmetic number, because the mean of its divisors is an integer number (8323103811).

Almost surely, 2^16646207621 is an apocalyptic number.

It is an amenable number.

16646207621 is a deficient number, since it is larger than the sum of its proper divisors (1).

16646207621 is an equidigital number, since it uses as much as digits as its factorization.

16646207621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 145152, while the sum is 41.

The spelling of 16646207621 in words is "sixteen billion, six hundred forty-six million, two hundred seven thousand, six hundred twenty-one".