31661021 has 8 divisors (see below), whose sum is σ = 38312640. Its totient is φ = 25541568.

The previous prime is 31661017. The next prime is 31661023. The reversal of 31661021 is 12016613.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 31661021 - 2² = 31661017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31660984 and 31661002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31661023) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 132911 + ... + 133148.

It is an arithmetic number, because the mean of its divisors is an integer number (4789080).

Almost surely, 2^31661021 is an apocalyptic number.

It is an amenable number.

31661021 is a deficient number, since it is larger than the sum of its proper divisors (6651619).

31661021 is a wasteful number, since it uses less digits than its factorization.

31661021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 266083.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 31661021 is about 5626.8126857040. The cubic root of 31661021 is about 316.3551959873.

Adding to 31661021 its reverse (12016613), we get a palindrome (43677634).

The spelling of 31661021 in words is "thirty-one million, six hundred sixty-one thousand, twenty-one".