28402421 has 4 divisors (see below), whose sum is σ = 29170092. Its totient is φ = 27634752.

The previous prime is 28402411. The next prime is 28402433. The reversal of 28402421 is 12420482.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12420482 = 2 ⋅6210241.

It can be written as a sum of positive squares in 2 ways, for example, as 18879025 + 9523396 = 4345^2 + 3086^2 .

It is a cyclic number.

It is not a de Polignac number, because 28402421 - 2⁶ = 28402357 is a prime.

It is a super-2 number, since 2×28402421² = 1613395037322482, 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 (28402411) 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, 383780 + ... + 383853.

It is an arithmetic number, because the mean of its divisors is an integer number (7292523).

Almost surely, 2^28402421 is an apocalyptic number.

It is an amenable number.

28402421 is a deficient number, since it is larger than the sum of its proper divisors (767671).

28402421 is an equidigital number, since it uses as much as digits as its factorization.

28402421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 767670.

The product of its (nonzero) digits is 1024, while the sum is 23.

The square root of 28402421 is about 5329.3921792264. The cubic root of 28402421 is about 305.1067296455.

The spelling of 28402421 in words is "twenty-eight million, four hundred two thousand, four hundred twenty-one".