21515523140351 has 4 divisors (see below), whose sum is σ = 21597331213392. Its totient is φ = 21433715067312.

The previous prime is 21515523140323. The next prime is 21515523140387. The reversal of 21515523140351 is 15304132551512.

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 21515523140351 - 2¹⁸ = 21515522878207 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21512523140351) 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, 40904036126 + ... + 40904036651.

It is an arithmetic number, because the mean of its divisors is an integer number (5399332803348).

Almost surely, 2^{21515523140351} is an apocalyptic number.

21515523140351 is a deficient number, since it is larger than the sum of its proper divisors (81808073041).

21515523140351 is an equidigital number, since it uses as much as digits as its factorization.

21515523140351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81808073040.

The product of its (nonzero) digits is 90000, while the sum is 38.

Adding to 21515523140351 its reverse (15304132551512), we get a palindrome (36819655691863).

The spelling of 21515523140351 in words is "twenty-one trillion, five hundred fifteen billion, five hundred twenty-three million, one hundred forty thousand, three hundred fifty-one".