21667540 has 12 divisors (see below), whose sum is σ = 45501876. Its totient is φ = 8667008.

The previous prime is 21667523. The next prime is 21667549. The reversal of 21667540 is 4576612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 4511376 + 17156164 = 2124^2 + 4142^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21667549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 541669 + ... + 541708.

It is an arithmetic number, because the mean of its divisors is an integer number (3791823).

Almost surely, 2^21667540 is an apocalyptic number.

21667540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21667540 is an abundant number, since it is smaller than the sum of its proper divisors (23834336).

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

21667540 is a wasteful number, since it uses less digits than its factorization.

21667540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1083386 (or 1083384 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 21667540 is about 4654.8404913595. The cubic root of 21667540 is about 278.7852992090.

The spelling of 21667540 in words is "twenty-one million, six hundred sixty-seven thousand, five hundred forty".