21155354110531 has 4 divisors (see below), whose sum is σ = 21554511735312. Its totient is φ = 20756196485752.

The previous prime is 21155354110481. The next prime is 21155354110549. The reversal of 21155354110531 is 13501145355112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21155354110531 is a prime.

It is a super-2 number, since 2×21155354110531² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21155354150531) 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, 199578812311 + ... + 199578812416.

It is an arithmetic number, because the mean of its divisors is an integer number (5388627933828).

Almost surely, 2^{21155354110531} is an apocalyptic number.

21155354110531 is a deficient number, since it is larger than the sum of its proper divisors (399157624781).

21155354110531 is an equidigital number, since it uses as much as digits as its factorization.

21155354110531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399157624780.

The product of its (nonzero) digits is 45000, while the sum is 37.

Adding to 21155354110531 its reverse (13501145355112), we get a palindrome (34656499465643).

The spelling of 21155354110531 in words is "twenty-one trillion, one hundred fifty-five billion, three hundred fifty-four million, one hundred ten thousand, five hundred thirty-one".