20345021 has 4 divisors (see below), whose sum is σ = 21001344. Its totient is φ = 19688700.

The previous prime is 20345011. The next prime is 20345023. The reversal of 20345021 is 12054302.

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 a de Polignac number, because none of the positive numbers 2^k-20345021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20345023) 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, 328115 + ... + 328176.

It is an arithmetic number, because the mean of its divisors is an integer number (5250336).

Almost surely, 2^20345021 is an apocalyptic number.

It is an amenable number.

20345021 is a deficient number, since it is larger than the sum of its proper divisors (656323).

20345021 is an equidigital number, since it uses as much as digits as its factorization.

20345021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 656322.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20345021 is about 4510.5455324162. The cubic root of 20345021 is about 272.9937562026.

Adding to 20345021 its reverse (12054302), we get a palindrome (32399323).

The spelling of 20345021 in words is "twenty million, three hundred forty-five thousand, twenty-one".