21395424640 has 128 divisors (see below), whose sum is σ = 53200425600. Its totient is φ = 8220745728.

The previous prime is 21395424637. The next prime is 21395424641. The reversal of 21395424640 is 4642459312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 21395424593 and 21395424602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21395424641) 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, 1865002 + ... + 1876438.

It is an arithmetic number, because the mean of its divisors is an integer number (415628325).

Almost surely, 2^21395424640 is an apocalyptic number.

21395424640 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 21395424640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26600212800).

21395424640 is an abundant number, since it is smaller than the sum of its proper divisors (31805000960).

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

21395424640 is a wasteful number, since it uses less digits than its factorization.

21395424640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11572 (or 11560 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 40.

The spelling of 21395424640 in words is "twenty-one billion, three hundred ninety-five million, four hundred twenty-four thousand, six hundred forty".