31985981 has 4 divisors (see below), whose sum is σ = 32006172. Its totient is φ = 31965792.

The previous prime is 31985971. The next prime is 31986013. The reversal of 31985981 is 18958913.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18958913 = 571 ⋅33203.

It can be written as a sum of positive squares in 2 ways, for example, as 19061956 + 12924025 = 4366^2 + 3595^2 .

It is a cyclic number.

It is not a de Polignac number, because 31985981 - 2⁶ = 31985917 is a prime.

It is a super-2 number, since 2×31985981² = 2046205961064722, 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 (31985951) 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, 7496 + ... + 10961.

It is an arithmetic number, because the mean of its divisors is an integer number (8001543).

Almost surely, 2^31985981 is an apocalyptic number.

It is an amenable number.

31985981 is a deficient number, since it is larger than the sum of its proper divisors (20191).

31985981 is a wasteful number, since it uses less digits than its factorization.

31985981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20190.

The product of its digits is 77760, while the sum is 44.

The square root of 31985981 is about 5655.6149975047. The cubic root of 31985981 is about 317.4338415897.

The spelling of 31985981 in words is "thirty-one million, nine hundred eighty-five thousand, nine hundred eighty-one".