21201323515 has 4 divisors (see below), whose sum is σ = 25441588224. Its totient is φ = 16961058808.

The previous prime is 21201323467. The next prime is 21201323537. The reversal of 21201323515 is 51532310212.

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

It is a cyclic number.

It is not a de Polignac number, because 21201323515 - 2¹³ = 21201315323 is a prime.

It is a super-2 number, since 2×21201323515² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21201323515.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2120132347 + ... + 2120132356.

It is an arithmetic number, because the mean of its divisors is an integer number (6360397056).

Almost surely, 2^21201323515 is an apocalyptic number.

21201323515 is a deficient number, since it is larger than the sum of its proper divisors (4240264709).

21201323515 is an equidigital number, since it uses as much as digits as its factorization.

21201323515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4240264708.

The product of its (nonzero) digits is 1800, while the sum is 25.

Adding to 21201323515 its reverse (51532310212), we get a palindrome (72733633727).

The spelling of 21201323515 in words is "twenty-one billion, two hundred one million, three hundred twenty-three thousand, five hundred fifteen".