28121731 has 6 divisors (see below), whose sum is σ = 30910796. Its totient is φ = 25565100.

The previous prime is 28121719. The next prime is 28121749. The reversal of 28121731 is 13712182.

It is a happy number.

It is not a de Polignac number, because 28121731 - 2⁷ = 28121603 is a prime.

It is a super-2 number, since 2×28121731² = 1581663508872722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 28121696 and 28121705.

It is not an unprimeable number, because it can be changed into a prime (28121761) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 116085 + ... + 116326.

Almost surely, 2^28121731 is an apocalyptic number.

28121731 is a deficient number, since it is larger than the sum of its proper divisors (2789065).

28121731 is a wasteful number, since it uses less digits than its factorization.

28121731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232433 (or 232422 counting only the distinct ones).

The product of its digits is 672, while the sum is 25.

The square root of 28121731 is about 5302.9926456672. The cubic root of 28121731 is about 304.0983169705.

The spelling of 28121731 in words is "twenty-eight million, one hundred twenty-one thousand, seven hundred thirty-one".