21406940 has 12 divisors (see below), whose sum is σ = 44954616. Its totient is φ = 8562768.

The previous prime is 21406933. The next prime is 21406963. The reversal of 21406940 is 4960412.

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, 535154 + ... + 535193.

It is an arithmetic number, because the mean of its divisors is an integer number (3746218).

Almost surely, 2^21406940 is an apocalyptic number.

21406940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21406940 is an abundant number, since it is smaller than the sum of its proper divisors (23547676).

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

21406940 is a wasteful number, since it uses less digits than its factorization.

21406940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1070356 (or 1070354 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21406940 is about 4626.7634475949. The cubic root of 21406940 is about 277.6631186635.

The spelling of 21406940 in words is "twenty-one million, four hundred six thousand, nine hundred forty".