21500034215251 has 4 divisors (see below), whose sum is σ = 21504073302712. Its totient is φ = 21495995127792.

The previous prime is 21500034215183. The next prime is 21500034215321. The reversal of 21500034215251 is 15251243000512.

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 21500034215251 - 2³³ = 21491444280659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21500034215951) 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, 2019535746 + ... + 2019546391.

It is an arithmetic number, because the mean of its divisors is an integer number (5376018325678).

Almost surely, 2^{21500034215251} is an apocalyptic number.

21500034215251 is a deficient number, since it is larger than the sum of its proper divisors (4039087461).

21500034215251 is an equidigital number, since it uses as much as digits as its factorization.

21500034215251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4039087460.

The product of its (nonzero) digits is 12000, while the sum is 31.

Adding to 21500034215251 its reverse (15251243000512), we get a palindrome (36751277215763).

The spelling of 21500034215251 in words is "twenty-one trillion, five hundred billion, thirty-four million, two hundred fifteen thousand, two hundred fifty-one".