21506238122915 has 24 divisors (see below), whose sum is σ = 32330256875280. Its totient is φ = 13612739732928.

The previous prime is 21506238122909. The next prime is 21506238122921. The reversal of 21506238122915 is 51922183260512.

It is an interprime number because it is at equal distance from previous prime (21506238122909) and next prime (21506238122921).

It is not a de Polignac number, because 21506238122915 - 2¹⁰ = 21506238121891 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21506238122915.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3376172345 + ... + 3376178714.

It is an arithmetic number, because the mean of its divisors is an integer number (1347094036470).

Almost surely, 2^{21506238122915} is an apocalyptic number.

21506238122915 is a deficient number, since it is larger than the sum of its proper divisors (10824018752365).

21506238122915 is a wasteful number, since it uses less digits than its factorization.

21506238122915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6752351091 (or 6752351084 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 47.

The spelling of 21506238122915 in words is "twenty-one trillion, five hundred six billion, two hundred thirty-eight million, one hundred twenty-two thousand, nine hundred fifteen".