20315021 has 4 divisors (see below), whose sum is σ = 20359932. Its totient is φ = 20270112.

The previous prime is 20315011. The next prime is 20315023. The reversal of 20315021 is 12051302.

It is a happy number.

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 10797796 + 9517225 = 3286^2 + 3085^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20315021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20314987 and 20315005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20315023) 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, 21770 + ... + 22683.

It is an arithmetic number, because the mean of its divisors is an integer number (5089983).

Almost surely, 2^20315021 is an apocalyptic number.

It is an amenable number.

20315021 is a deficient number, since it is larger than the sum of its proper divisors (44911).

20315021 is an equidigital number, since it uses as much as digits as its factorization.

20315021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44910.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 20315021 is about 4507.2187654916. The cubic root of 20315021 is about 272.8595080992.

Adding to 20315021 its reverse (12051302), we get a palindrome (32366323).

The spelling of 20315021 in words is "twenty million, three hundred fifteen thousand, twenty-one".