216403561 has 4 divisors (see below), whose sum is σ = 236076624. Its totient is φ = 196730500.

The previous prime is 216403553. The next prime is 216403567. The reversal of 216403561 is 165304612.

216403561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 216403561 - 2³ = 216403553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216403567) 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, 9836515 + ... + 9836536.

It is an arithmetic number, because the mean of its divisors is an integer number (59019156).

Almost surely, 2^216403561 is an apocalyptic number.

It is an amenable number.

216403561 is a deficient number, since it is larger than the sum of its proper divisors (19673063).

216403561 is a wasteful number, since it uses less digits than its factorization.

216403561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19673062.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 216403561 is about 14710.6614739107. The cubic root of 216403561 is about 600.3734351214.

The spelling of 216403561 in words is "two hundred sixteen million, four hundred three thousand, five hundred sixty-one".