21428279 has 4 divisors (see below), whose sum is σ = 22688784. Its totient is φ = 20167776.

The previous prime is 21428243. The next prime is 21428317. The reversal of 21428279 is 97282412.

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

It is a cyclic number.

It is not a de Polignac number, because 21428279 - 2²⁰ = 20379703 is a prime.

It is a super-2 number, since 2×21428279² = 918342281803682, 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 (21428579) 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, 630227 + ... + 630260.

It is an arithmetic number, because the mean of its divisors is an integer number (5672196).

Almost surely, 2^21428279 is an apocalyptic number.

21428279 is a deficient number, since it is larger than the sum of its proper divisors (1260505).

21428279 is a wasteful number, since it uses less digits than its factorization.

21428279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260504.

The product of its digits is 16128, while the sum is 35.

The square root of 21428279 is about 4629.0689128593. The cubic root of 21428279 is about 277.7553486542.

The spelling of 21428279 in words is "twenty-one million, four hundred twenty-eight thousand, two hundred seventy-nine".