31721418 has 48 divisors (see below), whose sum is σ = 72240480. Its totient is φ = 10045728.

The previous prime is 31721407. The next prime is 31721419. The reversal of 31721418 is 81412713.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 31721391 and 31721400.

It is not an unprimeable number, because it can be changed into a prime (31721419) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34521 + ... + 35427.

It is an arithmetic number, because the mean of its divisors is an integer number (1505010).

Almost surely, 2^31721418 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31721418, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36120240).

31721418 is an abundant number, since it is smaller than the sum of its proper divisors (40519062).

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

31721418 is a wasteful number, since it uses less digits than its factorization.

31721418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1011 (or 1008 counting only the distinct ones).

The product of its digits is 1344, while the sum is 27.

The square root of 31721418 is about 5632.1770213657. The cubic root of 31721418 is about 316.5562293874.

The spelling of 31721418 in words is "thirty-one million, seven hundred twenty-one thousand, four hundred eighteen".