21142840 has 32 divisors (see below), whose sum is σ = 48114000. Its totient is φ = 8360704.

The previous prime is 21142831. The next prime is 21142859. The reversal of 21142840 is 4824112.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 591 + ... + 6529.

Almost surely, 2^21142840 is an apocalyptic number.

21142840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21142840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24057000).

21142840 is an abundant number, since it is smaller than the sum of its proper divisors (26971160).

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

21142840 is a wasteful number, since it uses less digits than its factorization.

21142840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6039 (or 6035 counting only the distinct ones).

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

The square root of 21142840 is about 4598.1344042992. The cubic root of 21142840 is about 276.5165360216.

Adding to 21142840 its reverse (4824112), we get a palindrome (25966952).

The spelling of 21142840 in words is "twenty-one million, one hundred forty-two thousand, eight hundred forty".