21022840 has 16 divisors (see below), whose sum is σ = 47301480. Its totient is φ = 8409120.

The previous prime is 21022817. The next prime is 21022849. The reversal of 21022840 is 4822012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21022849) 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, 262746 + ... + 262825.

Almost surely, 2^21022840 is an apocalyptic number.

21022840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21022840 is an abundant number, since it is smaller than the sum of its proper divisors (26278640).

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

21022840 is a wasteful number, since it uses less digits than its factorization.

21022840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525582 (or 525578 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 21022840 is about 4585.0670660308. The cubic root of 21022840 is about 275.9924033476.

Adding to 21022840 its reverse (4822012), we get a palindrome (25844852).

The spelling of 21022840 in words is "twenty-one million, twenty-two thousand, eight hundred forty".