21906533 has 4 divisors (see below), whose sum is σ = 23898048. Its totient is φ = 19915020.

The previous prime is 21906509. The next prime is 21906541. The reversal of 21906533 is 33560912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21906533 - 2¹⁴ = 21890149 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21906496 and 21906505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906593) 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 3 ways as a sum of consecutive naturals, for example, 995741 + ... + 995762.

It is an arithmetic number, because the mean of its divisors is an integer number (5974512).

Almost surely, 2^21906533 is an apocalyptic number.

It is an amenable number.

21906533 is a deficient number, since it is larger than the sum of its proper divisors (1991515).

21906533 is a wasteful number, since it uses less digits than its factorization.

21906533 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1991514.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21906533 is about 4680.4415390004. The cubic root of 21906533 is about 279.8065543087.

The spelling of 21906533 in words is "twenty-one million, nine hundred six thousand, five hundred thirty-three".