21004415531 has 24 divisors (see below), whose sum is σ = 23551616592. Its totient is φ = 18711950400.

The previous prime is 21004415503. The next prime is 21004415563. The reversal of 21004415531 is 13551440012.

It is a de Polignac number, because none of the positive numbers 2^k-21004415531 is a prime.

It is a super-2 number, since 2×21004415531² (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 21004415531.

It is not an unprimeable number, because it can be changed into a prime (21004415591) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7508225 + ... + 7511021.

It is an arithmetic number, because the mean of its divisors is an integer number (981317358).

Almost surely, 2^21004415531 is an apocalyptic number.

21004415531 is a deficient number, since it is larger than the sum of its proper divisors (2547201061).

21004415531 is a wasteful number, since it uses less digits than its factorization.

21004415531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4043 (or 4032 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21004415531 its reverse (13551440012), we get a palindrome (34555855543).

The spelling of 21004415531 in words is "twenty-one billion, four million, four hundred fifteen thousand, five hundred thirty-one".