21543940 has 24 divisors (see below), whose sum is σ = 49355712. Its totient is φ = 7834080.

The previous prime is 21543931. The next prime is 21543961. The reversal of 21543940 is 4934512.

It is a junction number, because it is equal to n+sod(n) for n = 21543899 and 21543908.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48744 + ... + 49183.

It is an arithmetic number, because the mean of its divisors is an integer number (2056488).

Almost surely, 2^21543940 is an apocalyptic number.

21543940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21543940 is an abundant number, since it is smaller than the sum of its proper divisors (27811772).

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

21543940 is a wasteful number, since it uses less digits than its factorization.

21543940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97947 (or 97945 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21543940 is about 4641.5450013977. The cubic root of 21543940 is about 278.2541884364.

The spelling of 21543940 in words is "twenty-one million, five hundred forty-three thousand, nine hundred forty".