21553983 has 12 divisors (see below), whose sum is σ = 33964008. Its totient is φ = 13062960.

The previous prime is 21553969. The next prime is 21553997. The reversal of 21553983 is 38935512.

21553983 is a `hidden beast` number, since 21 + 553 + 9 + 83 = 666.

It is an interprime number because it is at equal distance from previous prime (21553969) and next prime (21553997).

It is not a de Polignac number, because 21553983 - 2⁵ = 21553951 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553933) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 108760 + ... + 108957.

It is an arithmetic number, because the mean of its divisors is an integer number (2830334).

Almost surely, 2^21553983 is an apocalyptic number.

21553983 is a deficient number, since it is larger than the sum of its proper divisors (12410025).

21553983 is a wasteful number, since it uses less digits than its factorization.

21553983 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217734 (or 217731 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 21553983 is about 4642.6267349422. The cubic root of 21553983 is about 278.2974190417.

The spelling of 21553983 in words is "twenty-one million, five hundred fifty-three thousand, nine hundred eighty-three".