21478856531 has 12 divisors (see below), whose sum is σ = 23614897992. Its totient is φ = 19521348000.

The previous prime is 21478856501. The next prime is 21478856543. The reversal of 21478856531 is 13565887412.

It is not a de Polignac number, because 21478856531 - 2³⁰ = 20405114707 is a prime.

It is a super-2 number, since 2×21478856531² (a number of 21 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 21478856531.

It is not an unprimeable number, because it can be changed into a prime (21478856501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 517376 + ... + 557346.

It is an arithmetic number, because the mean of its divisors is an integer number (1967908166).

Almost surely, 2^21478856531 is an apocalyptic number.

21478856531 is a deficient number, since it is larger than the sum of its proper divisors (2136041461).

21478856531 is a wasteful number, since it uses less digits than its factorization.

21478856531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44434 (or 44423 counting only the distinct ones).

The product of its digits is 1612800, while the sum is 50.

The spelling of 21478856531 in words is "twenty-one billion, four hundred seventy-eight million, eight hundred fifty-six thousand, five hundred thirty-one".