31661820 has 96 divisors (see below), whose sum is σ = 104328000. Its totient is φ = 7944192.

The previous prime is 31661801. The next prime is 31661821. The reversal of 31661820 is 2816613.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31661821) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7456 + ... + 10904.

It is an arithmetic number, because the mean of its divisors is an integer number (1086750).

Almost surely, 2^31661820 is an apocalyptic number.

31661820 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 31661820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (52164000).

31661820 is an abundant number, since it is smaller than the sum of its proper divisors (72666180).

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

31661820 is a wasteful number, since it uses less digits than its factorization.

31661820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3484 (or 3476 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 31661820 is about 5626.8836845984. The cubic root of 31661820 is about 316.3578571531.

The spelling of 31661820 in words is "thirty-one million, six hundred sixty-one thousand, eight hundred twenty".