31478721 has 4 divisors (see below), whose sum is σ = 41971632. Its totient is φ = 20985812.

The previous prime is 31478719. The next prime is 31478737. The reversal of 31478721 is 12787413.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 31478721 - 2¹ = 31478719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31478701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5246451 + ... + 5246456.

It is an arithmetic number, because the mean of its divisors is an integer number (10492908).

Almost surely, 2^31478721 is an apocalyptic number.

It is an amenable number.

31478721 is a deficient number, since it is larger than the sum of its proper divisors (10492911).

31478721 is a wasteful number, since it uses less digits than its factorization.

31478721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10492910.

The product of its digits is 9408, while the sum is 33.

The square root of 31478721 is about 5610.5900759189. The cubic root of 31478721 is about 315.7468496754.

The spelling of 31478721 in words is "thirty-one million, four hundred seventy-eight thousand, seven hundred twenty-one".