21521451539 has 8 divisors (see below), whose sum is σ = 25167943680. Its totient is φ = 18017959176.

The previous prime is 21521451517. The next prime is 21521451571. The reversal of 21521451539 is 93515412512.

It is a happy number.

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

It is not a de Polignac number, because 21521451539 - 2⁸ = 21521451283 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521451139) 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, 35749619 + ... + 35750220.

It is an arithmetic number, because the mean of its divisors is an integer number (3145992960).

Almost surely, 2^21521451539 is an apocalyptic number.

21521451539 is a deficient number, since it is larger than the sum of its proper divisors (3646492141).

21521451539 is an equidigital number, since it uses as much as digits as its factorization.

21521451539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71499889.

The product of its digits is 54000, while the sum is 38.

The spelling of 21521451539 in words is "twenty-one billion, five hundred twenty-one million, four hundred fifty-one thousand, five hundred thirty-nine".