31129921 has 8 divisors (see below), whose sum is σ = 32742144. Its totient is φ = 29555760.

The previous prime is 31129909. The next prime is 31129927. The reversal of 31129921 is 12992113.

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 31129921 - 2⁹ = 31129409 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 31129921.

It is not an unprimeable number, because it can be changed into a prime (31129927) 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, 7831 + ... + 11116.

It is an arithmetic number, because the mean of its divisors is an integer number (4092768).

Almost surely, 2^31129921 is an apocalyptic number.

31129921 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

It is an amenable number.

31129921 is a deficient number, since it is larger than the sum of its proper divisors (1612223).

31129921 is a wasteful number, since it uses less digits than its factorization.

31129921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19031.

The product of its digits is 972, while the sum is 28.

The square root of 31129921 is about 5579.4194142402. The cubic root of 31129921 is about 314.5763044651.

The spelling of 31129921 in words is "thirty-one million, one hundred twenty-nine thousand, nine hundred twenty-one".