20521109 has 4 divisors (see below), whose sum is σ = 23452704. Its totient is φ = 17589516.

The previous prime is 20521099. The next prime is 20521147. The reversal of 20521109 is 90112502.

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, and also an emirpimes, since its reverse is a distinct semiprime: 90112502 = 2 ⋅45056251.

It is a de Polignac number, because none of the positive numbers 2^k-20521109 is a prime.

It is a super-2 number, since 2×20521109² = 842231829179762, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521309) 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, 1465787 + ... + 1465800.

It is an arithmetic number, because the mean of its divisors is an integer number (5863176).

Almost surely, 2^20521109 is an apocalyptic number.

It is an amenable number.

20521109 is a deficient number, since it is larger than the sum of its proper divisors (2931595).

20521109 is an equidigital number, since it uses as much as digits as its factorization.

20521109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2931594.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 20521109 is about 4530.0230683739. The cubic root of 20521109 is about 273.7790900607.

The spelling of 20521109 in words is "twenty million, five hundred twenty-one thousand, one hundred nine".