28400781 has 8 divisors (see below), whose sum is σ = 38401344. Its totient is φ = 18667040.

The previous prime is 28400777. The next prime is 28400789. The reversal of 28400781 is 18700482.

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 28400781 - 2² = 28400777 is a prime.

It is a super-2 number, since 2×28400781² = 1613208722819922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28400789) 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 7 ways as a sum of consecutive naturals, for example, 66456 + ... + 66881.

It is an arithmetic number, because the mean of its divisors is an integer number (4800168).

Almost surely, 2^28400781 is an apocalyptic number.

It is an amenable number.

28400781 is a deficient number, since it is larger than the sum of its proper divisors (10000563).

28400781 is a wasteful number, since it uses less digits than its factorization.

28400781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133411.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 28400781 is about 5329.2383133052. The cubic root of 28400781 is about 305.1008570866.

The spelling of 28400781 in words is "twenty-eight million, four hundred thousand, seven hundred eighty-one".