31720721479 has 4 divisors (see below), whose sum is σ = 31822717680. Its totient is φ = 31618725280.

The previous prime is 31720721477. The next prime is 31720721497. The reversal of 31720721479 is 97412702713.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 31720721479 - 2¹ = 31720721477 is a prime.

It is a super-2 number, since 2×31720721479² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31720721477) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50997634 + ... + 50998255.

It is an arithmetic number, because the mean of its divisors is an integer number (7955679420).

Almost surely, 2^31720721479 is an apocalyptic number.

31720721479 is a deficient number, since it is larger than the sum of its proper divisors (101996201).

31720721479 is a wasteful number, since it uses less digits than its factorization.

31720721479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101996200.

The product of its (nonzero) digits is 148176, while the sum is 43.

The spelling of 31720721479 in words is "thirty-one billion, seven hundred twenty million, seven hundred twenty-one thousand, four hundred seventy-nine".