561481921 has 32 divisors (see below), whose sum is σ = 772321536. Its totient is φ = 393984000.

The previous prime is 561481903. The next prime is 561481961. The reversal of 561481921 is 129184165.

It is a 3-Lehmer number, since φ(561481921) divides (561481921-1)³.

It is a cyclic number.

It is a Carmichael number.

It is not a de Polignac number, because 561481921 - 2⁷ = 561481793 is a prime.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a deceptive number, since it divides R_561481920.

It is not an unprimeable number, because it can be changed into a prime (561481961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34201 + ... + 47881.

It is an arithmetic number, because the mean of its divisors is an integer number (24135048).

It is a Poulet number, since it divides 2^561481920-1.

Almost surely, 2^561481921 is an apocalyptic number.

561481921 is the 13681-st octagonal number.

It is an amenable number.

561481921 is a deficient number, since it is larger than the sum of its proper divisors (210839615).

561481921 is a wasteful number, since it uses less digits than its factorization.

561481921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13753.

The product of its digits is 17280, while the sum is 37.

The square root of 561481921 is about 23695.6097410470. The cubic root of 561481921 is about 824.9834932724.

The spelling of 561481921 in words is "five hundred sixty-one million, four hundred eighty-one thousand, nine hundred twenty-one".