21155356662431 has 4 divisors (see below), whose sum is σ = 21157970701992. Its totient is φ = 21152742622872.

The previous prime is 21155356662343. The next prime is 21155356662487. The reversal of 21155356662431 is 13426665355112.

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 21155356662431 - 2¹⁸ = 21155356400287 is a prime.

It is a super-2 number, since 2×21155356662431² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21155356662431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155356662031) 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, 1307007641 + ... + 1307023826.

It is an arithmetic number, because the mean of its divisors is an integer number (5289492675498).

Almost surely, 2^{21155356662431} is an apocalyptic number.

21155356662431 is a deficient number, since it is larger than the sum of its proper divisors (2614039561).

21155356662431 is an equidigital number, since it uses as much as digits as its factorization.

21155356662431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2614039560.

The product of its digits is 3888000, while the sum is 50.

The spelling of 21155356662431 in words is "twenty-one trillion, one hundred fifty-five billion, three hundred fifty-six million, six hundred sixty-two thousand, four hundred thirty-one".