28721644 has 18 divisors (see below), whose sum is σ = 58469460. Its totient is φ = 12309192.

The previous prime is 28721617. The next prime is 28721647. The reversal of 28721644 is 44612782.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (28721647) 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 5 ways as a sum of consecutive naturals, for example, 73074 + ... + 73465.

Almost surely, 2^28721644 is an apocalyptic number.

It is an amenable number.

28721644 is an abundant number, since it is smaller than the sum of its proper divisors (29747816).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28721644 is a wasteful number, since it uses less digits than its factorization.

28721644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146557 (or 146548 counting only the distinct ones).

The product of its digits is 21504, while the sum is 34.

The square root of 28721644 is about 5359.2577844325. The cubic root of 28721644 is about 306.2455346288.

The spelling of 28721644 in words is "twenty-eight million, seven hundred twenty-one thousand, six hundred forty-four".