21561152464 has 40 divisors (see below), whose sum is σ = 43230213000. Its totient is φ = 10405226496.

The previous prime is 21561152461. The next prime is 21561152477. The reversal of 21561152464 is 46425116512.

It can be written as a sum of positive squares in 4 ways, for example, as 942490000 + 20618662464 = 30700^2 + 143592^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561152461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1742652 + ... + 1754980.

It is an arithmetic number, because the mean of its divisors is an integer number (1080755325).

Almost surely, 2^21561152464 is an apocalyptic number.

It is an amenable number.

21561152464 is an abundant number, since it is smaller than the sum of its proper divisors (21669060536).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21561152464 is a wasteful number, since it uses less digits than its factorization.

21561152464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16135 (or 16129 counting only the distinct ones).

The product of its digits is 57600, while the sum is 37.

Adding to 21561152464 its reverse (46425116512), we get a palindrome (67986268976).

The spelling of 21561152464 in words is "twenty-one billion, five hundred sixty-one million, one hundred fifty-two thousand, four hundred sixty-four".