16205321621 has 8 divisors (see below), whose sum is σ = 17247483864. Its totient is φ = 15173038080.

The previous prime is 16205321591. The next prime is 16205321647. The reversal of 16205321621 is 12612350261.

It can be written as a sum of positive squares in 4 ways, for example, as 275095396 + 15930226225 = 16586^2 + 126215^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16205321621 - 2¹⁸ = 16205059477 is a prime.

It is a super-2 number, since 2×16205321621² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16205321681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2466290 + ... + 2472851.

It is an arithmetic number, because the mean of its divisors is an integer number (2155935483).

Almost surely, 2^16205321621 is an apocalyptic number.

It is an amenable number.

16205321621 is a deficient number, since it is larger than the sum of its proper divisors (1042162243).

16205321621 is a wasteful number, since it uses less digits than its factorization.

16205321621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4939351.

The product of its (nonzero) digits is 4320, while the sum is 29.

Adding to 16205321621 its reverse (12612350261), we get a palindrome (28817671882).

The spelling of 16205321621 in words is "sixteen billion, two hundred five million, three hundred twenty-one thousand, six hundred twenty-one".