21206940 has 48 divisors (see below), whose sum is σ = 59579520. Its totient is φ = 5636160.

The previous prime is 21206923. The next prime is 21206947. The reversal of 21206940 is 4960212.

It is a self number, because there is not a number n which added to its sum of digits gives 21206940.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33951 + ... + 34569.

It is an arithmetic number, because the mean of its divisors is an integer number (1241240).

Almost surely, 2^21206940 is an apocalyptic number.

21206940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21206940 is an abundant number, since it is smaller than the sum of its proper divisors (38372580).

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

21206940 is a wasteful number, since it uses less digits than its factorization.

21206940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1202 (or 1200 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21206940 is about 4605.0993474625. The cubic root of 21206940 is about 276.7956979462.

The spelling of 21206940 in words is "twenty-one million, two hundred six thousand, nine hundred forty".