20378521 has 4 divisors (see below), whose sum is σ = 20399652. Its totient is φ = 20357392.

The previous prime is 20378513. The next prime is 20378539. The reversal of 20378521 is 12587302.

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 1334025 + 19044496 = 1155^2 + 4364^2 .

It is a cyclic number.

It is not a de Polignac number, because 20378521 - 2³ = 20378513 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20378521.

It is not an unprimeable number, because it can be changed into a prime (20378221) 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, 9046 + ... + 11071.

It is an arithmetic number, because the mean of its divisors is an integer number (5099913).

Almost surely, 2^20378521 is an apocalyptic number.

It is an amenable number.

20378521 is a deficient number, since it is larger than the sum of its proper divisors (21131).

20378521 is a wasteful number, since it uses less digits than its factorization.

20378521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21130.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 20378521 is about 4514.2575247764. The cubic root of 20378521 is about 273.1435107116.

The spelling of 20378521 in words is "twenty million, three hundred seventy-eight thousand, five hundred twenty-one".