21403340 has 108 divisors (see below), whose sum is σ = 57043056. Its totient is φ = 6606336.

The previous prime is 21403337. The next prime is 21403399. The reversal of 21403340 is 4330412.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 930569 + ... + 930591.

Almost surely, 2^21403340 is an apocalyptic number.

21403340 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 21403340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28521528).

21403340 is an abundant number, since it is smaller than the sum of its proper divisors (35639716).

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

21403340 is a wasteful number, since it uses less digits than its factorization.

21403340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 54 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 17.

The square root of 21403340 is about 4626.3743903839. The cubic root of 21403340 is about 277.6475529441.

Adding to 21403340 its reverse (4330412), we get a palindrome (25733752).

The spelling of 21403340 in words is "twenty-one million, four hundred three thousand, three hundred forty".