20621609 has 2 divisors, whose sum is σ = 20621610. Its totient is φ = 20621608.

The previous prime is 20621597. The next prime is 20621677. The reversal of 20621609 is 90612602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 595984 = 4475^2 + 772^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20621609 is a prime.

It is not a weakly prime, because it can be changed into another prime (20621009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10310804 + 10310805.

It is an arithmetic number, because the mean of its divisors is an integer number (10310805).

Almost surely, 2^20621609 is an apocalyptic number.

It is an amenable number.

20621609 is a deficient number, since it is larger than the sum of its proper divisors (1).

20621609 is an equidigital number, since it uses as much as digits as its factorization.

20621609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 20621609 is about 4541.1021789869. The cubic root of 20621609 is about 274.2252973199.

The spelling of 20621609 in words is "twenty million, six hundred twenty-one thousand, six hundred nine".