16665026621 has 2 divisors, whose sum is σ = 16665026622. Its totient is φ = 16665026620.

The previous prime is 16665026591. The next prime is 16665026641. The reversal of 16665026621 is 12662056661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10570101721 + 6094924900 = 102811^2 + 78070^2 .

It is an emirp because it is prime and its reverse (12662056661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16665026621 - 2¹⁴ = 16665010237 is a prime.

It is a super-2 number, since 2×16665026621² (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 (16665026641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8332513310 + 8332513311.

It is an arithmetic number, because the mean of its divisors is an integer number (8332513311).

Almost surely, 2^16665026621 is an apocalyptic number.

It is an amenable number.

16665026621 is a deficient number, since it is larger than the sum of its proper divisors (1).

16665026621 is an equidigital number, since it uses as much as digits as its factorization.

16665026621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 155520, while the sum is 41.

The spelling of 16665026621 in words is "sixteen billion, six hundred sixty-five million, twenty-six thousand, six hundred twenty-one".