20809261 has 8 divisors (see below), whose sum is σ = 22750848. Its totient is φ = 18876000.

The previous prime is 20809249. The next prime is 20809279. The reversal of 20809261 is 16290802.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20809261 - 2¹⁹ = 20284973 is a prime.

It is a super-2 number, since 2×20809261² = 866050686732242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809361) 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 7 ways as a sum of consecutive naturals, for example, 3916 + ... + 7546.

It is an arithmetic number, because the mean of its divisors is an integer number (2843856).

Almost surely, 2^20809261 is an apocalyptic number.

It is an amenable number.

20809261 is a deficient number, since it is larger than the sum of its proper divisors (1941587).

20809261 is a wasteful number, since it uses less digits than its factorization.

20809261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4163.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 20809261 is about 4561.7168916977. The cubic root of 20809261 is about 275.0545831048.

The spelling of 20809261 in words is "twenty million, eight hundred nine thousand, two hundred sixty-one".