20705621 has 2 divisors, whose sum is σ = 20705622. Its totient is φ = 20705620.

The previous prime is 20705593. The next prime is 20705639. The reversal of 20705621 is 12650702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 2515396 = 4265^2 + 1586^2 .

It is a cyclic number.

It is not a de Polignac number, because 20705621 - 2⁶ = 20705557 is a prime.

It is a Chen prime.

It is equal to p_1312529 and since 20705621 and 1312529 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20705651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10352810 + 10352811.

It is an arithmetic number, because the mean of its divisors is an integer number (10352811).

Almost surely, 2^20705621 is an apocalyptic number.

It is an amenable number.

20705621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20705621 is an equidigital number, since it uses as much as digits as its factorization.

20705621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 20705621 is about 4550.3429541080. The cubic root of 20705621 is about 274.5971887755.

The spelling of 20705621 in words is "twenty million, seven hundred five thousand, six hundred twenty-one".