21408609551 has 48 divisors (see below), whose sum is σ = 25735034880. Its totient is φ = 17750839680.

The previous prime is 21408609539. The next prime is 21408609559. The reversal of 21408609551 is 15590680412.

It is not a de Polignac number, because 21408609551 - 2¹⁰ = 21408608527 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21408609499 and 21408609508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21408609559) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 75648656 + ... + 75648938.

It is an arithmetic number, because the mean of its divisors is an integer number (536146560).

Almost surely, 2^21408609551 is an apocalyptic number.

21408609551 is a deficient number, since it is larger than the sum of its proper divisors (4326425329).

21408609551 is a wasteful number, since it uses less digits than its factorization.

21408609551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 684 (or 677 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 41.

The spelling of 21408609551 in words is "twenty-one billion, four hundred eight million, six hundred nine thousand, five hundred fifty-one".