31213505 has 16 divisors (see below), whose sum is σ = 38755584. Its totient is φ = 24117120.

The previous prime is 31213487. The next prime is 31213531. The reversal of 31213505 is 50531213.

It is not a de Polignac number, because 31213505 - 2¹⁴ = 31197121 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21224 + ... + 22646.

It is an arithmetic number, because the mean of its divisors is an integer number (2422224).

Almost surely, 2^31213505 is an apocalyptic number.

It is an amenable number.

31213505 is a deficient number, since it is larger than the sum of its proper divisors (7542079).

31213505 is a wasteful number, since it uses less digits than its factorization.

31213505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1576.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 31213505 is about 5586.9047781397. The cubic root of 31213505 is about 314.8575991944.

Adding to 31213505 its reverse (50531213), we get a palindrome (81744718).

The spelling of 31213505 in words is "thirty-one million, two hundred thirteen thousand, five hundred five".