21531013 has 8 divisors (see below), whose sum is σ = 25676928. Its totient is φ = 17652624.

The previous prime is 21531011. The next prime is 21531023. The reversal of 21531013 is 31013512.

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

It is a cyclic number.

It is not a de Polignac number, because 21531013 - 2¹ = 21531011 is a prime.

It is a super-3 number, since 3×21531013³ (a number of 23 digits) contains 333 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 (21531011) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 66706 + ... + 67027.

It is an arithmetic number, because the mean of its divisors is an integer number (3209616).

Almost surely, 2^21531013 is an apocalyptic number.

21531013 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21531013 is a deficient number, since it is larger than the sum of its proper divisors (4145915).

21531013 is a wasteful number, since it uses less digits than its factorization.

21531013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133763.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21531013 is about 4640.1522604328. The cubic root of 21531013 is about 278.1985237257.

Adding to 21531013 its reverse (31013512), we get a palindrome (52544525).

The spelling of 21531013 in words is "twenty-one million, five hundred thirty-one thousand, thirteen".