20909761 has 4 divisors (see below), whose sum is σ = 21001300. Its totient is φ = 20818224.

The previous prime is 20909753. The next prime is 20909767. The reversal of 20909761 is 16790902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8526400 + 12383361 = 2920^2 + 3519^2 .

It is a cyclic number.

It is not a de Polignac number, because 20909761 - 2³ = 20909753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20909767) 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 in 3 ways as a sum of consecutive naturals, for example, 45426 + ... + 45883.

It is an arithmetic number, because the mean of its divisors is an integer number (5250325).

Almost surely, 2^20909761 is an apocalyptic number.

It is an amenable number.

20909761 is a deficient number, since it is larger than the sum of its proper divisors (91539).

20909761 is an equidigital number, since it uses as much as digits as its factorization.

20909761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91538.

The product of its (nonzero) digits is 6804, while the sum is 34.

The square root of 20909761 is about 4572.7192128973. The cubic root of 20909761 is about 275.4966715781.

The spelling of 20909761 in words is "twenty million, nine hundred nine thousand, seven hundred sixty-one".