21606440 has 32 divisors (see below), whose sum is σ = 48746880. Its totient is φ = 8619072.

The previous prime is 21606437. The next prime is 21606443. The reversal of 21606440 is 4460612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21606437) and next prime (21606443).

It is not an unprimeable number, because it can be changed into a prime (21606443) 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, 28709 + ... + 29451.

It is an arithmetic number, because the mean of its divisors is an integer number (1523340).

Almost surely, 2^21606440 is an apocalyptic number.

21606440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21606440 is an abundant number, since it is smaller than the sum of its proper divisors (27140440).

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

21606440 is a wasteful number, since it uses less digits than its factorization.

21606440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1481 (or 1477 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 21606440 is about 4648.2727975023. The cubic root of 21606440 is about 278.5230048888.

The spelling of 21606440 in words is "twenty-one million, six hundred six thousand, four hundred forty".