20280405 has 16 divisors (see below), whose sum is σ = 34357824. Its totient is φ = 10179840.

The previous prime is 20280401. The next prime is 20280413. The reversal of 20280405 is 50408202.

It is not a de Polignac number, because 20280405 - 2² = 20280401 is a prime.

It is a super-2 number, since 2×20280405² = 822589653928050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20280401) 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, 39511 + ... + 40020.

It is an arithmetic number, because the mean of its divisors is an integer number (2147364).

Almost surely, 2^20280405 is an apocalyptic number.

It is an amenable number.

20280405 is a deficient number, since it is larger than the sum of its proper divisors (14077419).

20280405 is a wasteful number, since it uses less digits than its factorization.

20280405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79556.

The product of its (nonzero) digits is 640, while the sum is 21.

The square root of 20280405 is about 4503.3770661582. The cubic root of 20280405 is about 272.7044393510.

Adding to 20280405 its reverse (50408202), we get a palindrome (70688607).

The spelling of 20280405 in words is "twenty million, two hundred eighty thousand, four hundred five".