21505143420031 has 16 divisors (see below), whose sum is σ = 21726117052416. Its totient is φ = 21285036644256.

The previous prime is 21505143420023. The next prime is 21505143420037. The reversal of 21505143420031 is 13002434150512.

It is a cyclic number.

It is not a de Polignac number, because 21505143420031 - 2³ = 21505143420023 is a prime.

It is a super-2 number, since 2×21505143420031² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21505143419975 and 21505143420002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505143420037) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 90925530 + ... + 91161736.

It is an arithmetic number, because the mean of its divisors is an integer number (1357882315776).

Almost surely, 2^{21505143420031} is an apocalyptic number.

21505143420031 is a deficient number, since it is larger than the sum of its proper divisors (220973632385).

21505143420031 is a wasteful number, since it uses less digits than its factorization.

21505143420031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 238038.

The product of its (nonzero) digits is 14400, while the sum is 31.

Adding to 21505143420031 its reverse (13002434150512), we get a palindrome (34507577570543).

The spelling of 21505143420031 in words is "twenty-one trillion, five hundred five billion, one hundred forty-three million, four hundred twenty thousand, thirty-one".