21403551440 has 80 divisors (see below), whose sum is σ = 51107260176. Its totient is φ = 8331264000.

The previous prime is 21403551343. The next prime is 21403551443. The reversal of 21403551440 is 4415530412.

It can be written as a sum of positive squares in 8 ways, for example, as 1729561744 + 19673989696 = 41588^2 + 140264^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×21403551440² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21403551443) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1307144 + ... + 1323416.

Almost surely, 2^21403551440 is an apocalyptic number.

21403551440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21403551440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25553630088).

21403551440 is an abundant number, since it is smaller than the sum of its proper divisors (29703708736).

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

21403551440 is a wasteful number, since it uses less digits than its factorization.

21403551440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16728 (or 16722 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 29.

The spelling of 21403551440 in words is "twenty-one billion, four hundred three million, five hundred fifty-one thousand, four hundred forty".