20815493 has 6 divisors (see below), whose sum is σ = 21135366. Its totient is φ = 20500392.

The previous prime is 20815481. The next prime is 20815517. The reversal of 20815493 is 39451802.

It can be written as a sum of positive squares in only one way, i.e., 15626209 + 5189284 = 3953^2 + 2278^2 .

It is not a de Polignac number, because 20815493 - 2¹² = 20811397 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 (20815453) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2171 + ... + 6807.

It is an arithmetic number, because the mean of its divisors is an integer number (3522561).

Almost surely, 2^20815493 is an apocalyptic number.

It is an amenable number.

20815493 is a deficient number, since it is larger than the sum of its proper divisors (319873).

20815493 is an frugal number, since it uses more digits than its factorization.

20815493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4771 (or 4704 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 20815493 is about 4562.3999167105. The cubic root of 20815493 is about 275.0820383337.

The spelling of 20815493 in words is "twenty million, eight hundred fifteen thousand, four hundred ninety-three".