31221420 has 24 divisors (see below), whose sum is σ = 87420144. Its totient is φ = 8325696.

The previous prime is 31221413. The next prime is 31221431. The reversal of 31221420 is 2412213.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 31221420.

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, 260119 + ... + 260238.

It is an arithmetic number, because the mean of its divisors is an integer number (3642506).

Almost surely, 2^31221420 is an apocalyptic number.

31221420 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

31221420 is an abundant number, since it is smaller than the sum of its proper divisors (56198724).

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

31221420 is a wasteful number, since it uses less digits than its factorization.

31221420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520369 (or 520367 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 31221420 is about 5587.6130861039. The cubic root of 31221420 is about 314.8842104030.

Adding to 31221420 its reverse (2412213), we get a palindrome (33633633).

The spelling of 31221420 in words is "thirty-one million, two hundred twenty-one thousand, four hundred twenty".