20491261 has 6 divisors (see below), whose sum is σ = 23836830. Its totient is φ = 17563896.

The previous prime is 20491243. The next prime is 20491277. The reversal of 20491261 is 16219402.

It can be written as a sum of positive squares in only one way, i.e., 11431161 + 9060100 = 3381^2 + 3010^2 .

It is not a de Polignac number, because 20491261 - 2⁹ = 20490749 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20491561) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 209046 + ... + 209143.

It is an arithmetic number, because the mean of its divisors is an integer number (3972805).

Almost surely, 2^20491261 is an apocalyptic number.

It is an amenable number.

20491261 is a deficient number, since it is larger than the sum of its proper divisors (3345569).

20491261 is an equidigital number, since it uses as much as digits as its factorization.

20491261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 418203 (or 418196 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20491261 is about 4526.7274050908. The cubic root of 20491261 is about 273.6462882154.

The spelling of 20491261 in words is "twenty million, four hundred ninety-one thousand, two hundred sixty-one".