20404240 has 20 divisors (see below), whose sum is σ = 47440044. Its totient is φ = 8161664.

The previous prime is 20404213. The next prime is 20404249. The reversal of 20404240 is 4240402.

It can be written as a sum of positive squares in 2 ways, for example, as 10061584 + 10342656 = 3172^2 + 3216^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is not an unprimeable number, because it can be changed into a prime (20404249) 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, 127447 + ... + 127606.

Almost surely, 2^20404240 is an apocalyptic number.

20404240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20404240 is an abundant number, since it is smaller than the sum of its proper divisors (27035804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20404240 is a wasteful number, since it uses less digits than its factorization.

20404240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255066 (or 255060 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 16.

The square root of 20404240 is about 4517.1052677572. The cubic root of 20404240 is about 273.2583706123.

Adding to 20404240 its reverse (4240402), we get a palindrome (24644642).

The spelling of 20404240 in words is "twenty million, four hundred four thousand, two hundred forty".