216413521 has 9 divisors (see below), whose sum is σ = 221824731. Its totient is φ = 211132272.

The previous prime is 216413507. The next prime is 216413531. The reversal of 216413521 is 125314612.

It is a happy number.

The square root of 216413521 is 14711.

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

216413521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 1380625 + 215032896 = 1175^2 + 14664^2 .

It is not a de Polignac number, because 216413521 - 2¹¹ = 216411473 is a prime.

It is a Duffinian number.

Its product of digits (1440) is a multiple of the sum of its prime divisors (360).

It is not an unprimeable number, because it can be changed into a prime (216413531) 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, 691261 + ... + 691573.

Almost surely, 2^216413521 is an apocalyptic number.

216413521 is the 14711-st square number.

216413521 is the 7356-th centered octagonal number.

It is an amenable number.

216413521 is a deficient number, since it is larger than the sum of its proper divisors (5411210).

216413521 is an frugal number, since it uses more digits than its factorization.

216413521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 720 (or 360 counting only the distinct ones).

The product of its digits is 1440, while the sum is 25.

The cubic root of 216413521 is about 600.3826457333.

Multiplying 216413521 by its sum of digits (25), we get a square (5410338025 = 73555²).

The spelling of 216413521 in words is "two hundred sixteen million, four hundred thirteen thousand, five hundred twenty-one".