21001013 has 4 divisors (see below), whose sum is σ = 22910208. Its totient is φ = 19091820.

The previous prime is 21000983. The next prime is 21001021. The reversal of 21001013 is 31010012.

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 21001013 - 2¹⁴ = 20984629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001033) 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 3 ways as a sum of consecutive naturals, for example, 954581 + ... + 954602.

It is an arithmetic number, because the mean of its divisors is an integer number (5727552).

Almost surely, 2^21001013 is an apocalyptic number.

It is an amenable number.

21001013 is a deficient number, since it is larger than the sum of its proper divisors (1909195).

21001013 is a wasteful number, since it uses less digits than its factorization.

21001013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1909194.

The product of its (nonzero) digits is 6, while the sum is 8.

The square root of 21001013 is about 4582.6862209844. The cubic root of 21001013 is about 275.8968537417.

Adding to 21001013 its reverse (31010012), we get a palindrome (52011025).

It can be divided in two parts, 2100 and 1013, that added together give a palindrome (3113).

The spelling of 21001013 in words is "twenty-one million, one thousand, thirteen".