21406040 has 16 divisors (see below), whose sum is σ = 48163680. Its totient is φ = 8562400.

The previous prime is 21406037. The next prime is 21406069. The reversal of 21406040 is 4060412.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 267536 + ... + 267615.

It is an arithmetic number, because the mean of its divisors is an integer number (3010230).

Almost surely, 2^21406040 is an apocalyptic number.

21406040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21406040 is an abundant number, since it is smaller than the sum of its proper divisors (26757640).

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

21406040 is a wasteful number, since it uses less digits than its factorization.

21406040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 535162 (or 535158 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21406040 is about 4626.6661863592. Note that the first 3 decimals coincide. The cubic root of 21406040 is about 277.6592273973.

Adding to 21406040 its reverse (4060412), we get a palindrome (25466452).

The spelling of 21406040 in words is "twenty-one million, four hundred six thousand, forty".