20405131 has 4 divisors (see below), whose sum is σ = 20607264. Its totient is φ = 20203000.

The previous prime is 20405129. The next prime is 20405137. The reversal of 20405131 is 13150402.

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

It is a cyclic number.

It is not a de Polignac number, because 20405131 - 2¹ = 20405129 is a prime.

It is a super-2 number, since 2×20405131² = 832738742254322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20405137) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 100915 + ... + 101116.

It is an arithmetic number, because the mean of its divisors is an integer number (5151816).

Almost surely, 2^20405131 is an apocalyptic number.

20405131 is a deficient number, since it is larger than the sum of its proper divisors (202133).

20405131 is a wasteful number, since it uses less digits than its factorization.

20405131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 202132.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 20405131 is about 4517.2038917897. The cubic root of 20405131 is about 273.2623480481.

Adding to 20405131 its reverse (13150402), we get a palindrome (33555533).

The spelling of 20405131 in words is "twenty million, four hundred five thousand, one hundred thirty-one".