28772821 has 32 divisors (see below), whose sum is σ = 38430720. Its totient is φ = 20865600.

The previous prime is 28772797. The next prime is 28772831. The reversal of 28772821 is 12827782.

It is a happy number.

It is not a de Polignac number, because 28772821 - 2²³ = 20384213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28772831) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 103735 + ... + 104011.

It is an arithmetic number, because the mean of its divisors is an integer number (1200960).

Almost surely, 2^28772821 is an apocalyptic number.

It is an amenable number.

28772821 is a deficient number, since it is larger than the sum of its proper divisors (9657899).

28772821 is a wasteful number, since it uses less digits than its factorization.

28772821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 385.

The product of its digits is 25088, while the sum is 37.

The square root of 28772821 is about 5364.0302944708. The cubic root of 28772821 is about 306.4273188868.

The spelling of 28772821 in words is "twenty-eight million, seven hundred seventy-two thousand, eight hundred twenty-one".