31661999 has 4 divisors (see below), whose sum is σ = 33328440. Its totient is φ = 29995560.

The previous prime is 31661983. The next prime is 31662013. The reversal of 31661999 is 99916613.

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: 99916613 = 37 ⋅2700449.

It is a cyclic number.

It is not a de Polignac number, because 31661999 - 2⁴ = 31661983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31661909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 833192 + ... + 833229.

It is an arithmetic number, because the mean of its divisors is an integer number (8332110).

Almost surely, 2^31661999 is an apocalyptic number.

31661999 is a deficient number, since it is larger than the sum of its proper divisors (1666441).

31661999 is a wasteful number, since it uses less digits than its factorization.

31661999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1666440.

The product of its digits is 78732, while the sum is 44.

The square root of 31661999 is about 5626.8995903606. The cubic root of 31661999 is about 316.3584533280.

The spelling of 31661999 in words is "thirty-one million, six hundred sixty-one thousand, nine hundred ninety-nine".