20402521 has 2 divisors, whose sum is σ = 20402522. Its totient is φ = 20402520.

The previous prime is 20402513. The next prime is 20402531. The reversal of 20402521 is 12520402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20115225 + 287296 = 4485^2 + 536^2 .

It is a cyclic number.

It is not a de Polignac number, because 20402521 - 2³ = 20402513 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20402495 and 20402504.

It is not a weakly prime, because it can be changed into another prime (20402531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10201260 + 10201261.

It is an arithmetic number, because the mean of its divisors is an integer number (10201261).

Almost surely, 2^20402521 is an apocalyptic number.

It is an amenable number.

20402521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20402521 is an equidigital number, since it uses as much as digits as its factorization.

20402521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 20402521 is about 4516.9149870238. The cubic root of 20402521 is about 273.2506966464.

Adding to 20402521 its reverse (12520402), we get a palindrome (32922923).

The spelling of 20402521 in words is "twenty million, four hundred two thousand, five hundred twenty-one".