21284140 has 24 divisors (see below), whose sum is σ = 45738000. Its totient is φ = 8315328.

The previous prime is 21284129. The next prime is 21284141. The reversal of 21284140 is 4148212.

21284140 = T₄₀₉ + T₄₁₀ + ... + T₅₈₀.

It is not an unprimeable number, because it can be changed into a prime (21284141) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11515 + ... + 13234.

It is an arithmetic number, because the mean of its divisors is an integer number (1905750).

Almost surely, 2^21284140 is an apocalyptic number.

21284140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21284140 is an abundant number, since it is smaller than the sum of its proper divisors (24453860).

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

21284140 is a wasteful number, since it uses less digits than its factorization.

21284140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24801 (or 24799 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 22.

The square root of 21284140 is about 4613.4737454547. The cubic root of 21284140 is about 277.1311659685.

The spelling of 21284140 in words is "twenty-one million, two hundred eighty-four thousand, one hundred forty".