21942020 has 12 divisors (see below), whose sum is σ = 46078284. Its totient is φ = 8776800.

The previous prime is 21942007. The next prime is 21942029. The reversal of 21942020 is 2024912.

It can be written as a sum of positive squares in 2 ways, for example, as 2458624 + 19483396 = 1568^2 + 4414^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1097101 = 21942020 / (2 + 1 + 9 + 4 + 2 + 0 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 21941983 and 21942001.

It is not an unprimeable number, because it can be changed into a prime (21942029) 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, 548531 + ... + 548570.

It is an arithmetic number, because the mean of its divisors is an integer number (3839857).

Almost surely, 2^21942020 is an apocalyptic number.

21942020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21942020 is an abundant number, since it is smaller than the sum of its proper divisors (24136264).

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

21942020 is a wasteful number, since it uses less digits than its factorization.

21942020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1097110 (or 1097108 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21942020 is about 4684.2309934503. The cubic root of 21942020 is about 279.9575615953.

Subtracting from 21942020 its sum of digits (20), we obtain a triangular number (21942000 = T₆₆₂₄).

Adding to 21942020 its reverse (2024912), we get a palindrome (23966932).

The spelling of 21942020 in words is "twenty-one million, nine hundred forty-two thousand, twenty".