31220640 has 288 divisors, whose sum is σ = 122181696. Its totient is φ = 7464960.

The previous prime is 31220633. The next prime is 31220641. The reversal of 31220640 is 4602213.

It is a happy number.

31220640 is a `hidden beast` number, since 3 + 1 + 2 + 20 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (31220641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 427644 + ... + 427716.

It is an arithmetic number, because the mean of its divisors is an integer number (424242).

Almost surely, 2^31220640 is an apocalyptic number.

31220640 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 31220640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (61090848).

31220640 is an abundant number, since it is smaller than the sum of its proper divisors (90961056).

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

31220640 is a wasteful number, since it uses less digits than its factorization.

31220640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114 (or 94 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 31220640 is about 5587.5432884229. The cubic root of 31220640 is about 314.8815881464.

Adding to 31220640 its reverse (4602213), we get a palindrome (35822853).

The spelling of 31220640 in words is "thirty-one million, two hundred twenty thousand, six hundred forty".