21555956 has 12 divisors (see below), whose sum is σ = 39708480. Its totient is φ = 10210680.

The previous prime is 21555931. The next prime is 21555967. The reversal of 21555956 is 65955512.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 141740 + ... + 141891.

It is an arithmetic number, because the mean of its divisors is an integer number (3309040).

Almost surely, 2^21555956 is an apocalyptic number.

It is an amenable number.

21555956 is a deficient number, since it is larger than the sum of its proper divisors (18152524).

21555956 is a wasteful number, since it uses less digits than its factorization.

21555956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283654 (or 283652 counting only the distinct ones).

The product of its digits is 67500, while the sum is 38.

The square root of 21555956 is about 4642.8392175478. The cubic root of 21555956 is about 278.3059103424.

The spelling of 21555956 in words is "twenty-one million, five hundred fifty-five thousand, nine hundred fifty-six".