20689521 has 4 divisors (see below), whose sum is σ = 27586032. Its totient is φ = 13793012.

The previous prime is 20689519. The next prime is 20689523. The reversal of 20689521 is 12598602.

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 an interprime number because it is at equal distance from previous prime (20689519) and next prime (20689523).

It is a cyclic number.

It is not a de Polignac number, because 20689521 - 2¹ = 20689519 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20689523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3448251 + ... + 3448256.

It is an arithmetic number, because the mean of its divisors is an integer number (6896508).

Almost surely, 2^20689521 is an apocalyptic number.

It is an amenable number.

20689521 is a deficient number, since it is larger than the sum of its proper divisors (6896511).

20689521 is an equidigital number, since it uses as much as digits as its factorization.

20689521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6896510.

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 20689521 is about 4548.5735126521. The cubic root of 20689521 is about 274.5259977832.

The spelling of 20689521 in words is "twenty million, six hundred eighty-nine thousand, five hundred twenty-one".