21930521 has 4 divisors (see below), whose sum is σ = 21949200. Its totient is φ = 21911844.

The previous prime is 21930511. The next prime is 21930553. The reversal of 21930521 is 12503912.

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 21930521 - 2⁶ = 21930457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21930511) 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, 7451 + ... + 9968.

It is an arithmetic number, because the mean of its divisors is an integer number (5487300).

Almost surely, 2^21930521 is an apocalyptic number.

It is an amenable number.

21930521 is a deficient number, since it is larger than the sum of its proper divisors (18679).

21930521 is a wasteful number, since it uses less digits than its factorization.

21930521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18678.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21930521 is about 4683.0034166120. The cubic root of 21930521 is about 279.9086479200.

The spelling of 21930521 in words is "twenty-one million, nine hundred thirty thousand, five hundred twenty-one".