20721631 has 8 divisors (see below), whose sum is σ = 24498720. Its totient is φ = 17148768.

The previous prime is 20721629. The next prime is 20721637. The reversal of 20721631 is 13612702.

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

It is not a de Polignac number, because 20721631 - 2¹ = 20721629 is a prime.

It is a super-2 number, since 2×20721631² = 858771982600322, 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 (20721637) 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 7 ways as a sum of consecutive naturals, for example, 50836 + ... + 51241.

It is an arithmetic number, because the mean of its divisors is an integer number (3062340).

Almost surely, 2^20721631 is an apocalyptic number.

20721631 is a deficient number, since it is larger than the sum of its proper divisors (3777089).

20721631 is a wasteful number, since it uses less digits than its factorization.

20721631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102113.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 20721631 is about 4552.1018222355. The cubic root of 20721631 is about 274.6679452201.

The spelling of 20721631 in words is "twenty million, seven hundred twenty-one thousand, six hundred thirty-one".