20837521 has 2 divisors, whose sum is σ = 20837522. Its totient is φ = 20837520.

The previous prime is 20837519. The next prime is 20837543. The reversal of 20837521 is 12573802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15249025 + 5588496 = 3905^2 + 2364^2 .

It is a cyclic number.

It is not a de Polignac number, because 20837521 - 2¹ = 20837519 is a prime.

Together with 20837519, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 20837521.

It is not a weakly prime, because it can be changed into another prime (20837581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10418760 + 10418761.

It is an arithmetic number, because the mean of its divisors is an integer number (10418761).

Almost surely, 2^20837521 is an apocalyptic number.

It is an amenable number.

20837521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20837521 is an equidigital number, since it uses as much as digits as its factorization.

20837521 is an evil number, because the sum of its binary digits is even.

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

The square root of 20837521 is about 4564.8133587256. The cubic root of 20837521 is about 275.1790393336.

It can be divided in two parts, 2083 and 7521, that added together give a square (9604 = 98²).

The spelling of 20837521 in words is "twenty million, eight hundred thirty-seven thousand, five hundred twenty-one".