21640742 has 8 divisors (see below), whose sum is σ = 32643000. Its totient is φ = 10759744.

The previous prime is 21640721. The next prime is 21640747. The reversal of 21640742 is 24704612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640747) 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 3 ways as a sum of consecutive naturals, for example, 29867 + ... + 30582.

It is an arithmetic number, because the mean of its divisors is an integer number (4080375).

Almost surely, 2^21640742 is an apocalyptic number.

21640742 is a deficient number, since it is larger than the sum of its proper divisors (11002258).

21640742 is a wasteful number, since it uses less digits than its factorization.

21640742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60630.

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21640742 is about 4651.9610918407. The cubic root of 21640742 is about 278.6703196818.

The spelling of 21640742 in words is "twenty-one million, six hundred forty thousand, seven hundred forty-two".