16508285915521 has 9 divisors (see below), whose sum is σ = 16680627180099. Its totient is φ = 16337707349184.

The previous prime is 16508285915519. The next prime is 16508285915551. The reversal of 16508285915521 is 12551958280561.

It is a happy number.

The square root of 16508285915521 is 4063039.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7412850249025 + 9095435666496 = 2722655^2 + 3015864^2 .

It is not a de Polignac number, because 16508285915521 - 2¹ = 16508285915519 is a prime.

It is a super-2 number, since 2×16508285915521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16508285915551) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 394093840 + ... + 394135726.

It is an arithmetic number, because the mean of its divisors is an integer number (1853403020011).

Almost surely, 2^{16508285915521} is an apocalyptic number.

16508285915521 is the 4063039-th square number.

16508285915521 is the 2031520-th centered octagonal number.

It is an amenable number.

16508285915521 is a deficient number, since it is larger than the sum of its proper divisors (172341264578).

16508285915521 is an frugal number, since it uses more digits than its factorization.

16508285915521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83968 (or 41984 counting only the distinct ones).

The product of its (nonzero) digits is 8640000, while the sum is 58.

The spelling of 16508285915521 in words is "sixteen trillion, five hundred eight billion, two hundred eighty-five million, nine hundred fifteen thousand, five hundred twenty-one".