21002631 has 8 divisors (see below), whose sum is σ = 30157680. Its totient is φ = 12924672.

The previous prime is 21002629. The next prime is 21002651. The reversal of 21002631 is 13620012.

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

It is not a de Polignac number, because 21002631 - 2¹ = 21002629 is a prime.

It is a super-2 number, since 2×21002631² = 882221017844322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21002631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 269226 + ... + 269303.

It is an arithmetic number, because the mean of its divisors is an integer number (3769710).

Almost surely, 2^21002631 is an apocalyptic number.

21002631 is a deficient number, since it is larger than the sum of its proper divisors (9155049).

21002631 is a wasteful number, since it uses less digits than its factorization.

21002631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538545.

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21002631 is about 4582.8627515997. The cubic root of 21002631 is about 275.9039389498.

Adding to 21002631 its reverse (13620012), we get a palindrome (34622643).

The spelling of 21002631 in words is "twenty-one million, two thousand, six hundred thirty-one".