21573963 has 6 divisors (see below), whose sum is σ = 31162404. Its totient is φ = 14382636.

The previous prime is 21573907. The next prime is 21573971. The reversal of 21573963 is 36937512.

21573963 is a `hidden beast` number, since 21 + 573 + 9 + 63 = 666.

It is not a de Polignac number, because 21573963 - 2⁸ = 21573707 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21573973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1198545 + ... + 1198562.

It is an arithmetic number, because the mean of its divisors is an integer number (5193734).

Almost surely, 2^21573963 is an apocalyptic number.

21573963 is a deficient number, since it is larger than the sum of its proper divisors (9588441).

21573963 is a wasteful number, since it uses less digits than its factorization.

21573963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2397113 (or 2397110 counting only the distinct ones).

The product of its digits is 34020, while the sum is 36.

The square root of 21573963 is about 4644.7780356008. The cubic root of 21573963 is about 278.3833840534.

The spelling of 21573963 in words is "twenty-one million, five hundred seventy-three thousand, nine hundred sixty-three".