28172421 has 16 divisors (see below), whose sum is σ = 43934400. Its totient is φ = 17792784.

The previous prime is 28172407. The next prime is 28172437. The reversal of 28172421 is 12427182.

It is not a de Polignac number, because 28172421 - 2⁶ = 28172357 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28172461) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26946 + ... + 27971.

It is an arithmetic number, because the mean of its divisors is an integer number (2745900).

Almost surely, 2^28172421 is an apocalyptic number.

It is an amenable number.

28172421 is a deficient number, since it is larger than the sum of its proper divisors (15761979).

28172421 is a wasteful number, since it uses less digits than its factorization.

28172421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54945 (or 54939 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 28172421 is about 5307.7698706707. The cubic root of 28172421 is about 304.2809217938.

The spelling of 28172421 in words is "twenty-eight million, one hundred seventy-two thousand, four hundred twenty-one".