28715381 has 4 divisors (see below), whose sum is σ = 28827372. Its totient is φ = 28603392.

The previous prime is 28715377. The next prime is 28715387. The reversal of 28715381 is 18351782.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18351782 = 2 ⋅9175891.

It can be written as a sum of positive squares in 2 ways, for example, as 24850225 + 3865156 = 4985^2 + 1966^2 .

It is a cyclic number.

It is not a de Polignac number, because 28715381 - 2² = 28715377 is a prime.

It is a super-2 number, since 2×28715381² = 1649146211950322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28715387) 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, 55610 + ... + 56123.

It is an arithmetic number, because the mean of its divisors is an integer number (7206843).

Almost surely, 2^28715381 is an apocalyptic number.

It is an amenable number.

28715381 is a deficient number, since it is larger than the sum of its proper divisors (111991).

28715381 is a wasteful number, since it uses less digits than its factorization.

28715381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111990.

The product of its digits is 13440, while the sum is 35.

The square root of 28715381 is about 5358.6734365886. The cubic root of 28715381 is about 306.2232731917.

The spelling of 28715381 in words is "twenty-eight million, seven hundred fifteen thousand, three hundred eighty-one".