20121405 has 16 divisors (see below), whose sum is σ = 32880384. Its totient is φ = 10502720.

The previous prime is 20121401. The next prime is 20121427. The reversal of 20121405 is 50412102.

It is not a de Polignac number, because 20121405 - 2² = 20121401 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20121401) 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 15 ways as a sum of consecutive naturals, for example, 13566 + ... + 14975.

It is an arithmetic number, because the mean of its divisors is an integer number (2055024).

Almost surely, 2^20121405 is an apocalyptic number.

It is an amenable number.

20121405 is a deficient number, since it is larger than the sum of its proper divisors (12758979).

20121405 is a wasteful number, since it uses less digits than its factorization.

20121405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28596.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 20121405 is about 4485.6889103013. The cubic root of 20121405 is about 271.9898938359.

Adding to 20121405 its reverse (50412102), we get a palindrome (70533507).

The spelling of 20121405 in words is "twenty million, one hundred twenty-one thousand, four hundred five".