31440 has 40 divisors (see below), whose sum is σ = 98208. Its totient is φ = 8320.
The previous prime is 31397. The next prime is 31469. The reversal of 31440 is 4413.
31440 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.
It is a tau number, because it is divible by the number of its divisors (40).
It is a Harshad number since it is a multiple of its sum of digits (12).
It is a nialpdrome in base 8.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 31440.
It is an unprimeable number.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175 + ... + 305.
231440 is an apocalyptic number.
31440 is a gapful number since it is divisible by the number (30) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 31440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49104).
31440 is an abundant number, since it is smaller than the sum of its proper divisors (66768).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
31440 is a wasteful number, since it uses less digits than its factorization.
31440 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 147 (or 141 counting only the distinct ones).
The product of its (nonzero) digits is 48, while the sum is 12.
The square root of 31440 is about 177.3132820744. The cubic root of 31440 is about 31.5617333082.
Adding to 31440 its reverse (4413), we get a palindrome (35853).
The spelling of 31440 in words is "thirty-one thousand, four hundred forty".
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