28077721 has 4 divisors (see below), whose sum is σ = 32088832. Its totient is φ = 24066612.

The previous prime is 28077719. The next prime is 28077767. The reversal of 28077721 is 12777082.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28077721 - 2¹ = 28077719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28077701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2005545 + ... + 2005558.

It is an arithmetic number, because the mean of its divisors is an integer number (8022208).

Almost surely, 2^28077721 is an apocalyptic number.

It is an amenable number.

28077721 is a deficient number, since it is larger than the sum of its proper divisors (4011111).

28077721 is an equidigital number, since it uses as much as digits as its factorization.

28077721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4011110.

The product of its (nonzero) digits is 10976, while the sum is 34.

The square root of 28077721 is about 5298.8414771533. The cubic root of 28077721 is about 303.9395980237.

The spelling of 28077721 in words is "twenty-eight million, seventy-seven thousand, seven hundred twenty-one".