31121840 has 20 divisors (see below), whose sum is σ = 72358464. Its totient is φ = 12448704.

The previous prime is 31121833. The next prime is 31121869. The reversal of 31121840 is 4812113.

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 (20).

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 194432 + ... + 194591.

Almost surely, 2^31121840 is an apocalyptic number.

It is an amenable number.

31121840 is an abundant number, since it is smaller than the sum of its proper divisors (41236624).

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

31121840 is a wasteful number, since it uses less digits than its factorization.

31121840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389036 (or 389030 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 31121840 is about 5578.6951879449. The cubic root of 31121840 is about 314.5490818763.

Adding to 31121840 its reverse (4812113), we get a palindrome (35933953).

The spelling of 31121840 in words is "thirty-one million, one hundred twenty-one thousand, eight hundred forty".