15561216 has 120 divisors (see below), whose sum is σ = 49153104. Its totient is φ = 4700160.

The previous prime is 15561211. The next prime is 15561229. The reversal of 15561216 is 61216551.

It is a happy number.

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 15561216.

It is not an unprimeable number, because it can be changed into a prime (15561211) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 50535 + ... + 50841.

Almost surely, 2^15561216 is an apocalyptic number.

15561216 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 15561216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24576552).

15561216 is an abundant number, since it is smaller than the sum of its proper divisors (33591888).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

15561216 is a wasteful number, since it uses less digits than its factorization.

15561216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342 (or 323 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 15561216 is about 3944.7707157704. The cubic root of 15561216 is about 249.6593547207.

Adding to 15561216 its reverse (61216551), we get a palindrome (76777767).

It can be divided in two parts, 1556 and 1216, that added together give a palindrome (2772).

The spelling of 15561216 in words is "fifteen million, five hundred sixty-one thousand, two hundred sixteen".