21406215531 has 8 divisors (see below), whose sum is σ = 28542475584. Its totient is φ = 14270382920.

The previous prime is 21406215359. The next prime is 21406215541. The reversal of 21406215531 is 13551260412.

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

It is a cyclic number.

It is not a de Polignac number, because 21406215531 - 2¹¹ = 21406213483 is a prime.

It is a super-2 number, since 2×21406215531² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21406215541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38080 + ... + 210386.

It is an arithmetic number, because the mean of its divisors is an integer number (3567809448).

Almost surely, 2^21406215531 is an apocalyptic number.

21406215531 is a deficient number, since it is larger than the sum of its proper divisors (7136260053).

21406215531 is a wasteful number, since it uses less digits than its factorization.

21406215531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213721.

The product of its (nonzero) digits is 7200, while the sum is 30.

Adding to 21406215531 its reverse (13551260412), we get a palindrome (34957475943).

The spelling of 21406215531 in words is "twenty-one billion, four hundred six million, two hundred fifteen thousand, five hundred thirty-one".