21871956671551 has 8 divisors (see below), whose sum is σ = 25244012227104. Its totient is φ = 18561773695200.

The previous prime is 21871956671527. The next prime is 21871956671569. The reversal of 21871956671551 is 15517665917812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21871956671551 - 2¹⁵ = 21871956638783 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 (21871956671051) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15468144040 + ... + 15468145453.

It is an arithmetic number, because the mean of its divisors is an integer number (3155501528388).

Almost surely, 2^{21871956671551} is an apocalyptic number.

21871956671551 is a deficient number, since it is larger than the sum of its proper divisors (3372055555553).

21871956671551 is a wasteful number, since it uses less digits than its factorization.

21871956671551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30936289601.

The product of its digits is 31752000, while the sum is 64.

The spelling of 21871956671551 in words is "twenty-one trillion, eight hundred seventy-one billion, nine hundred fifty-six million, six hundred seventy-one thousand, five hundred fifty-one".