21501013 has 4 divisors (see below), whose sum is σ = 21698380. Its totient is φ = 21303648.

The previous prime is 21500953. The next prime is 21501023. The reversal of 21501013 is 31010512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19421649 + 2079364 = 4407^2 + 1442^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21501013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21500984 and 21501002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21501023) 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, 98520 + ... + 98737.

It is an arithmetic number, because the mean of its divisors is an integer number (5424595).

Almost surely, 2^21501013 is an apocalyptic number.

It is an amenable number.

21501013 is a deficient number, since it is larger than the sum of its proper divisors (197367).

21501013 is a wasteful number, since it uses less digits than its factorization.

21501013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197366.

The product of its (nonzero) digits is 30, while the sum is 13.

The square root of 21501013 is about 4636.9184810605. The cubic root of 21501013 is about 278.0692553851.

Adding to 21501013 its reverse (31010512), we get a palindrome (52511525).

The spelling of 21501013 in words is "twenty-one million, five hundred one thousand, thirteen".