21428280 has 64 divisors (see below), whose sum is σ = 71431200. Its totient is φ = 5713920.

The previous prime is 21428243. The next prime is 21428317. The reversal of 21428280 is 8282412.

It is an interprime number because it is at equal distance from previous prime (21428243) and next prime (21428317).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8841 + ... + 11000.

Almost surely, 2^21428280 is an apocalyptic number.

21428280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21428280 is an abundant number, since it is smaller than the sum of its proper divisors (50002920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21428280 is a wasteful number, since it uses less digits than its factorization.

21428280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19861 (or 19851 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 21428280 is about 4629.0690208723. The cubic root of 21428280 is about 277.7553529749.

The spelling of 21428280 in words is "twenty-one million, four hundred twenty-eight thousand, two hundred eighty".