28137421 has 4 divisors (see below), whose sum is σ = 30301852. Its totient is φ = 25972992.

The previous prime is 28137419. The next prime is 28137433. The reversal of 28137421 is 12473182.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19053225 + 9084196 = 4365^2 + 3014^2 .

It is a cyclic number.

It is not a de Polignac number, because 28137421 - 2¹ = 28137419 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28137421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28137401) 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, 1082196 + ... + 1082221.

It is an arithmetic number, because the mean of its divisors is an integer number (7575463).

Almost surely, 2^28137421 is an apocalyptic number.

It is an amenable number.

28137421 is a deficient number, since it is larger than the sum of its proper divisors (2164431).

28137421 is a wasteful number, since it uses less digits than its factorization.

28137421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2164430.

The product of its digits is 2688, while the sum is 28.

The square root of 28137421 is about 5304.4717927424. The cubic root of 28137421 is about 304.1548618008.

The spelling of 28137421 in words is "twenty-eight million, one hundred thirty-seven thousand, four hundred twenty-one".