31638729 has 4 divisors (see below), whose sum is σ = 42184976. Its totient is φ = 21092484.

The previous prime is 31638709. The next prime is 31638779. The reversal of 31638729 is 92783613.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 31638729 - 2⁵ = 31638697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31638709) 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, 5273119 + ... + 5273124.

It is an arithmetic number, because the mean of its divisors is an integer number (10546244).

Almost surely, 2^31638729 is an apocalyptic number.

It is an amenable number.

31638729 is a deficient number, since it is larger than the sum of its proper divisors (10546247).

31638729 is a wasteful number, since it uses less digits than its factorization.

31638729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10546246.

The product of its digits is 54432, while the sum is 39.

The square root of 31638729 is about 5624.8314641418. The cubic root of 31638729 is about 316.2809317389.

The spelling of 31638729 in words is "thirty-one million, six hundred thirty-eight thousand, seven hundred twenty-nine".