20406531 has 4 divisors (see below), whose sum is σ = 27208712. Its totient is φ = 13604352.

The previous prime is 20406523. The next prime is 20406539. The reversal of 20406531 is 13560402.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (20406523) and next prime (20406539).

It is not a de Polignac number, because 20406531 - 2³ = 20406523 is a prime.

It is a super-4 number, since 4×20406531⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20406498 and 20406507.

It is not an unprimeable number, because it can be changed into a prime (20406539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3401086 + ... + 3401091.

It is an arithmetic number, because the mean of its divisors is an integer number (6802178).

Almost surely, 2^20406531 is an apocalyptic number.

20406531 is a deficient number, since it is larger than the sum of its proper divisors (6802181).

20406531 is an equidigital number, since it uses as much as digits as its factorization.

20406531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6802180.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 20406531 is about 4517.3588522498. The cubic root of 20406531 is about 273.2685974328.

Adding to 20406531 its reverse (13560402), we get a palindrome (33966933).

The spelling of 20406531 in words is "twenty million, four hundred six thousand, five hundred thirty-one".