21340040 has 64 divisors (see below), whose sum is σ = 51796800. Its totient is φ = 7886592.

The previous prime is 21340019. The next prime is 21340051. The reversal of 21340040 is 4004312.

It is a junction number, because it is equal to n+sod(n) for n = 21339997 and 21340024.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32354 + ... + 33006.

It is an arithmetic number, because the mean of its divisors is an integer number (809325).

Almost surely, 2^21340040 is an apocalyptic number.

21340040 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 21340040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25898400).

21340040 is an abundant number, since it is smaller than the sum of its proper divisors (30456760).

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

21340040 is a wasteful number, since it uses less digits than its factorization.

21340040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 726 (or 722 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21340040 is about 4619.5281144290. The cubic root of 21340040 is about 277.3735700886.

Adding to 21340040 its reverse (4004312), we get a palindrome (25344352).

The spelling of 21340040 in words is "twenty-one million, three hundred forty thousand, forty".