28780561 has 8 divisors (see below), whose sum is σ = 29634984. Its totient is φ = 27930240.

The previous prime is 28780559. The next prime is 28780571. The reversal of 28780561 is 16508782.

It can be written as a sum of positive squares in 4 ways, for example, as 12531600 + 16248961 = 3540^2 + 4031^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28780561 - 2¹ = 28780559 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28780561.

It is not an unprimeable number, because it can be changed into a prime (28780571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18531 + ... + 20023.

It is an arithmetic number, because the mean of its divisors is an integer number (3704373).

Almost surely, 2^28780561 is an apocalyptic number.

It is an amenable number.

28780561 is a deficient number, since it is larger than the sum of its proper divisors (854423).

28780561 is a wasteful number, since it uses less digits than its factorization.

28780561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2051.

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 28780561 is about 5364.7517183929. The cubic root of 28780561 is about 306.4547931342.

The spelling of 28780561 in words is "twenty-eight million, seven hundred eighty thousand, five hundred sixty-one".