21404340 has 36 divisors (see below), whose sum is σ = 64927044. Its totient is φ = 5707776.

The previous prime is 21404321. The next prime is 21404359. The reversal of 21404340 is 4340412.

It is an interprime number because it is at equal distance from previous prime (21404321) and next prime (21404359).

It can be written as a sum of positive squares in 2 ways, for example, as 3663396 + 17740944 = 1914^2 + 4212^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59277 + ... + 59636.

It is an arithmetic number, because the mean of its divisors is an integer number (1803529).

Almost surely, 2^21404340 is an apocalyptic number.

21404340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21404340 is an abundant number, since it is smaller than the sum of its proper divisors (43522704).

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

21404340 is a wasteful number, since it uses less digits than its factorization.

21404340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118928 (or 118923 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21404340 is about 4626.4824651132. The cubic root of 21404340 is about 277.6518769301.

Adding to 21404340 its reverse (4340412), we get a palindrome (25744752).

The spelling of 21404340 in words is "twenty-one million, four hundred four thousand, three hundred forty".