216561541 has 4 divisors (see below), whose sum is σ = 247498912. Its totient is φ = 185624172.

The previous prime is 216561533. The next prime is 216561547. The reversal of 216561541 is 145165612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216561541 - 2³ = 216561533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216561547) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15468675 + ... + 15468688.

It is an arithmetic number, because the mean of its divisors is an integer number (61874728).

Almost surely, 2^216561541 is an apocalyptic number.

It is an amenable number.

216561541 is a deficient number, since it is larger than the sum of its proper divisors (30937371).

216561541 is an equidigital number, since it uses as much as digits as its factorization.

216561541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30937370.

The product of its digits is 7200, while the sum is 31.

The square root of 216561541 is about 14716.0300692816. The cubic root of 216561541 is about 600.5194954480.

The spelling of 216561541 in words is "two hundred sixteen million, five hundred sixty-one thousand, five hundred forty-one".