20405501 has 2 divisors, whose sum is σ = 20405502. Its totient is φ = 20405500.

The previous prime is 20405479. The next prime is 20405513. The reversal of 20405501 is 10550402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13697401 + 6708100 = 3701^2 + 2590^2 .

It is a cyclic number.

It is not a de Polignac number, because 20405501 - 2²² = 16211197 is a prime.

It is a super-2 number, since 2×20405501² = 832768942122002, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20405501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20405551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10202750 + 10202751.

It is an arithmetic number, because the mean of its divisors is an integer number (10202751).

Almost surely, 2^20405501 is an apocalyptic number.

It is an amenable number.

20405501 is a deficient number, since it is larger than the sum of its proper divisors (1).

20405501 is an equidigital number, since it uses as much as digits as its factorization.

20405501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 200, while the sum is 17.

The square root of 20405501 is about 4517.2448461424. The cubic root of 20405501 is about 273.2639996990.

Adding to 20405501 its reverse (10550402), we get a palindrome (30955903).

The spelling of 20405501 in words is "twenty million, four hundred five thousand, five hundred one".