31721989 has 4 divisors (see below), whose sum is σ = 34162156. Its totient is φ = 29281824.

The previous prime is 31721953. The next prime is 31722049. The reversal of 31721989 is 98912713.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98912713 = 647 ⋅152879.

It can be written as a sum of positive squares in 2 ways, for example, as 1361889 + 30360100 = 1167^2 + 5510^2 .

It is not a de Polignac number, because 31721989 - 2⁷ = 31721861 is a prime.

It is a super-2 number, since 2×31721989² = 2012569172232242, which 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 (31727989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1220064 + ... + 1220089.

It is an arithmetic number, because the mean of its divisors is an integer number (8540539).

Almost surely, 2^31721989 is an apocalyptic number.

It is an amenable number.

31721989 is a deficient number, since it is larger than the sum of its proper divisors (2440167).

31721989 is a wasteful number, since it uses less digits than its factorization.

31721989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2440166.

The product of its digits is 27216, while the sum is 40.

The square root of 31721989 is about 5632.2277120159. The cubic root of 31721989 is about 316.5581287615.

The spelling of 31721989 in words is "thirty-one million, seven hundred twenty-one thousand, nine hundred eighty-nine".