21340240 has 40 divisors (see below), whose sum is σ = 50440968. Its totient is φ = 8394240.

The previous prime is 21340223. The next prime is 21340243. The reversal of 21340240 is 4204312.

It can be written as a sum of positive squares in 4 ways, for example, as 69696 + 21270544 = 264^2 + 4612^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21340243) 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, 2694 + ... + 7066.

Almost surely, 2^21340240 is an apocalyptic number.

21340240 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 21340240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25220484).

21340240 is an abundant number, since it is smaller than the sum of its proper divisors (29100728).

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

21340240 is a wasteful number, since it uses less digits than its factorization.

21340240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4447 (or 4441 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21340240 is about 4619.5497616110. The cubic root of 21340240 is about 277.3744366059.

Adding to 21340240 its reverse (4204312), we get a palindrome (25544552).

It can be divided in two parts, 21340 and 240, that multiplied together give a triangular number (5121600 = T₃₂₀₀).

The spelling of 21340240 in words is "twenty-one million, three hundred forty thousand, two hundred forty".