28721578685 has 16 divisors (see below), whose sum is σ = 35671978800. Its totient is φ = 22173989376.

The previous prime is 28721578681. The next prime is 28721578723. The reversal of 28721578685 is 58687512782.

It can be written as a sum of positive squares in 8 ways, for example, as 247716121 + 28473862564 = 15739^2 + 168742^2 .

It is a cyclic number.

It is not a de Polignac number, because 28721578685 - 2² = 28721578681 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28721578681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 252137 + ... + 347873.

It is an arithmetic number, because the mean of its divisors is an integer number (2229498675).

Almost surely, 2^28721578685 is an apocalyptic number.

It is an amenable number.

28721578685 is a deficient number, since it is larger than the sum of its proper divisors (6950400115).

28721578685 is a wasteful number, since it uses less digits than its factorization.

28721578685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97840.

The product of its digits is 15052800, while the sum is 59.

The spelling of 28721578685 in words is "twenty-eight billion, seven hundred twenty-one million, five hundred seventy-eight thousand, six hundred eighty-five".