100405561 has 4 divisors (see below), whose sum is σ = 100445824. Its totient is φ = 100365300.

The previous prime is 100405549. The next prime is 100405589. The reversal of 100405561 is 165504001.

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 100405561 - 2⁹ = 100405049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (100405541) 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, 16125 + ... + 21466.

It is an arithmetic number, because the mean of its divisors is an integer number (25111456).

Almost surely, 2^100405561 is an apocalyptic number.

It is an amenable number.

100405561 is a deficient number, since it is larger than the sum of its proper divisors (40263).

100405561 is an equidigital number, since it uses as much as digits as its factorization.

100405561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40262.

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 100405561 is about 10020.2575316206. The cubic root of 100405561 is about 464.7855194623.

Adding to 100405561 its reverse (165504001), we get a palindrome (265909562).

The spelling of 100405561 in words is "one hundred million, four hundred five thousand, five hundred sixty-one".