21515453420243 has 4 divisors (see below), whose sum is σ = 21551372374800. Its totient is φ = 21479534465688.

The previous prime is 21515453420203. The next prime is 21515453420249. The reversal of 21515453420243 is 34202435451512.

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 21515453420243 - 2²² = 21515449225939 is a prime.

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 21515453420243.

It is not an unprimeable number, because it can be changed into a prime (21515453420249) 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, 17959476380 + ... + 17959477577.

It is an arithmetic number, because the mean of its divisors is an integer number (5387843093700).

Almost surely, 2^{21515453420243} is an apocalyptic number.

21515453420243 is a deficient number, since it is larger than the sum of its proper divisors (35918954557).

21515453420243 is an equidigital number, since it uses as much as digits as its factorization.

21515453420243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35918954556.

The product of its (nonzero) digits is 576000, while the sum is 41.

Adding to 21515453420243 its reverse (34202435451512), we get a palindrome (55717888871755).

The spelling of 21515453420243 in words is "twenty-one trillion, five hundred fifteen billion, four hundred fifty-three million, four hundred twenty thousand, two hundred forty-three".