20021537 has 2 divisors, whose sum is σ = 20021538. Its totient is φ = 20021536.

The previous prime is 20021527. The next prime is 20021539. The reversal of 20021537 is 73512002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12967201 + 7054336 = 3601^2 + 2656^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20021537 is a prime.

Together with 20021539, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20021539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010768 + 10010769.

It is an arithmetic number, because the mean of its divisors is an integer number (10010769).

Almost surely, 2^20021537 is an apocalyptic number.

It is an amenable number.

20021537 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021537 is an equidigital number, since it uses as much as digits as its factorization.

20021537 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 20021537 is about 4474.5432169105. The cubic root of 20021537 is about 271.5391607268.

Adding to 20021537 its reverse (73512002), we get a palindrome (93533539).

The spelling of 20021537 in words is "twenty million, twenty-one thousand, five hundred thirty-seven".