21745642 has 8 divisors (see below), whose sum is σ = 32688000. Its totient is φ = 10849644.

The previous prime is 21745639. The next prime is 21745643. The reversal of 21745642 is 24654712.

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

It is not an unprimeable number, because it can be changed into a prime (21745643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10392 + ... + 12307.

It is an arithmetic number, because the mean of its divisors is an integer number (4086000).

Almost surely, 2^21745642 is an apocalyptic number.

21745642 is a deficient number, since it is larger than the sum of its proper divisors (10942358).

21745642 is a wasteful number, since it uses less digits than its factorization.

21745642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23180.

The product of its digits is 13440, while the sum is 31.

The square root of 21745642 is about 4663.2222764951. Note that the first 4 decimals coincide. The cubic root of 21745642 is about 279.1198638798.

The spelling of 21745642 in words is "twenty-one million, seven hundred forty-five thousand, six hundred forty-two".