20421745 has 4 divisors (see below), whose sum is σ = 24506100. Its totient is φ = 16337392.

The previous prime is 20421733. The next prime is 20421749. The reversal of 20421745 is 54712402.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12737761 + 7683984 = 3569^2 + 2772^2 .

It is a cyclic number.

It is not a de Polignac number, because 20421745 - 2¹¹ = 20419697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20421749) 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, 2042170 + ... + 2042179.

It is an arithmetic number, because the mean of its divisors is an integer number (6126525).

Almost surely, 2^20421745 is an apocalyptic number.

It is an amenable number.

20421745 is a deficient number, since it is larger than the sum of its proper divisors (4084355).

20421745 is an equidigital number, since it uses as much as digits as its factorization.

20421745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4084354.

The product of its (nonzero) digits is 2240, while the sum is 25.

The square root of 20421745 is about 4519.0424870762. The cubic root of 20421745 is about 273.3364919656.

The spelling of 20421745 in words is "twenty million, four hundred twenty-one thousand, seven hundred forty-five".