28391669 has 4 divisors (see below), whose sum is σ = 28494444. Its totient is φ = 28288896.

The previous prime is 28391663. The next prime is 28391677. The reversal of 28391669 is 96619382.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 96619382 = 2 ⋅48309691.

It can be written as a sum of positive squares in 2 ways, for example, as 13468900 + 14922769 = 3670^2 + 3863^2 .

It is a cyclic number.

It is not a de Polignac number, because 28391669 - 2¹² = 28387573 is a prime.

It is a super-2 number, since 2×28391669² = 1612173737211122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28391663) 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, 50972 + ... + 51525.

It is an arithmetic number, because the mean of its divisors is an integer number (7123611).

Almost surely, 2^28391669 is an apocalyptic number.

It is an amenable number.

28391669 is a deficient number, since it is larger than the sum of its proper divisors (102775).

28391669 is a wasteful number, since it uses less digits than its factorization.

28391669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102774.

The product of its digits is 139968, while the sum is 44.

The square root of 28391669 is about 5328.3833383119. The cubic root of 28391669 is about 305.0682244585.

The spelling of 28391669 in words is "twenty-eight million, three hundred ninety-one thousand, six hundred sixty-nine".