21543660 has 36 divisors (see below), whose sum is σ = 65349648. Its totient is φ = 5744928.

The previous prime is 21543659. The next prime is 21543677. The reversal of 21543660 is 6634512.

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 59664 + ... + 60023.

It is an arithmetic number, because the mean of its divisors is an integer number (1815268).

Almost surely, 2^21543660 is an apocalyptic number.

21543660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21543660 is an abundant number, since it is smaller than the sum of its proper divisors (43805988).

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

21543660 is a wasteful number, since it uses less digits than its factorization.

21543660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119702 (or 119697 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21543660 is about 4641.5148389292. The cubic root of 21543660 is about 278.2529829697.

It can be divided in two parts, 215436 and 60, that added together give a triangular number (215496 = T₆₅₆).

The spelling of 21543660 in words is "twenty-one million, five hundred forty-three thousand, six hundred sixty".