20531440 has 20 divisors (see below), whose sum is σ = 47735784. Its totient is φ = 8212544.

The previous prime is 20531437. The next prime is 20531477. The reversal of 20531440 is 4413502.

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

It is a congruent number.

It is an unprimeable number.

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, 128242 + ... + 128401.

Almost surely, 2^20531440 is an apocalyptic number.

20531440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20531440 is an abundant number, since it is smaller than the sum of its proper divisors (27204344).

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

20531440 is a wasteful number, since it uses less digits than its factorization.

20531440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256656 (or 256650 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 20531440 is about 4531.1632060653. The cubic root of 20531440 is about 273.8250254806.

Adding to 20531440 its reverse (4413502), we get a palindrome (24944942).

The spelling of 20531440 in words is "twenty million, five hundred thirty-one thousand, four hundred forty".