21515454044215 has 4 divisors (see below), whose sum is σ = 25818544853064. Its totient is φ = 17212363235368.

The previous prime is 21515454044173. The next prime is 21515454044233. The reversal of 21515454044215 is 51244045451512.

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 21515454044215 - 2⁹ = 21515454043703 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 2151545404417 + ... + 2151545404426.

It is an arithmetic number, because the mean of its divisors is an integer number (6454636213266).

Almost surely, 2^{21515454044215} is an apocalyptic number.

21515454044215 is a deficient number, since it is larger than the sum of its proper divisors (4303090808849).

21515454044215 is an equidigital number, since it uses as much as digits as its factorization.

21515454044215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4303090808848.

The product of its (nonzero) digits is 640000, while the sum is 43.

Adding to 21515454044215 its reverse (51244045451512), we get a palindrome (72759499495727).

The spelling of 21515454044215 in words is "twenty-one trillion, five hundred fifteen billion, four hundred fifty-four million, forty-four thousand, two hundred fifteen".