31779921 has 4 divisors (see below), whose sum is σ = 42373232. Its totient is φ = 21186612.

The previous prime is 31779907. The next prime is 31779941. The reversal of 31779921 is 12997713.

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 not a de Polignac number, because 31779921 - 2⁵ = 31779889 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31779921.

It is not an unprimeable number, because it can be changed into a prime (31779901) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 5296651 + ... + 5296656.

It is an arithmetic number, because the mean of its divisors is an integer number (10593308).

Almost surely, 2^31779921 is an apocalyptic number.

It is an amenable number.

31779921 is a deficient number, since it is larger than the sum of its proper divisors (10593311).

31779921 is a wasteful number, since it uses less digits than its factorization.

31779921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10593310.

The product of its digits is 23814, while the sum is 39.

The square root of 31779921 is about 5637.3682689709. The cubic root of 31779921 is about 316.7507153940.

The spelling of 31779921 in words is "thirty-one million, seven hundred seventy-nine thousand, nine hundred twenty-one".