21505534431 has 8 divisors (see below), whose sum is σ = 28776089904. Its totient is φ = 14286000960.

The previous prime is 21505534417. The next prime is 21505534433. The reversal of 21505534431 is 13443550512.

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

It is not a de Polignac number, because 21505534431 - 2¹⁵ = 21505501663 is a prime.

It is a super-2 number, since 2×21505534431² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21505534392 and 21505534401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505534433) 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, 12754516 + ... + 12756201.

It is an arithmetic number, because the mean of its divisors is an integer number (3597011238).

Almost surely, 2^21505534431 is an apocalyptic number.

21505534431 is a deficient number, since it is larger than the sum of its proper divisors (7270555473).

21505534431 is a wasteful number, since it uses less digits than its factorization.

21505534431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25511001.

The product of its (nonzero) digits is 36000, while the sum is 33.

The spelling of 21505534431 in words is "twenty-one billion, five hundred five million, five hundred thirty-four thousand, four hundred thirty-one".