21666342 has 16 divisors (see below), whose sum is σ = 44255232. Its totient is φ = 7068360.

The previous prime is 21666341. The next prime is 21666343. The reversal of 21666342 is 24366612.

It is an interprime number because it is at equal distance from previous prime (21666341) and next prime (21666343).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38134 + ... + 38697.

It is an arithmetic number, because the mean of its divisors is an integer number (2765952).

Almost surely, 2^21666342 is an apocalyptic number.

21666342 is an abundant number, since it is smaller than the sum of its proper divisors (22588890).

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

21666342 is a wasteful number, since it uses less digits than its factorization.

21666342 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76883.

The product of its digits is 10368, while the sum is 30.

The square root of 21666342 is about 4654.7118063313. The cubic root of 21666342 is about 278.7801610939.

The spelling of 21666342 in words is "twenty-one million, six hundred sixty-six thousand, three hundred forty-two".