21404431616 has 72 divisors (see below), whose sum is σ = 44708853504. Its totient is φ = 10214830080.

The previous prime is 21404431613. The next prime is 21404431639. The reversal of 21404431616 is 61613440412.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404431613) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 560855 + ... + 597801.

Almost surely, 2^21404431616 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21404431616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22354426752).

21404431616 is an abundant number, since it is smaller than the sum of its proper divisors (23304421888).

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

21404431616 is an equidigital number, since it uses as much as digits as its factorization.

21404431616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37067 (or 37053 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 32.

The spelling of 21404431616 in words is "twenty-one billion, four hundred four million, four hundred thirty-one thousand, six hundred sixteen".