21742138 has 8 divisors (see below), whose sum is σ = 35578080. Its totient is φ = 9882780.

The previous prime is 21742111. The next prime is 21742139. The reversal of 21742138 is 83124712.

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

It is a super-2 number, since 2×21742138² = 945441129622088, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21742139) 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, 494118 + ... + 494161.

It is an arithmetic number, because the mean of its divisors is an integer number (4447260).

Almost surely, 2^21742138 is an apocalyptic number.

21742138 is a deficient number, since it is larger than the sum of its proper divisors (13835942).

21742138 is a wasteful number, since it uses less digits than its factorization.

21742138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 988292.

The product of its digits is 2688, while the sum is 28.

The square root of 21742138 is about 4662.8465554852. The cubic root of 21742138 is about 279.1048710130.

The spelling of 21742138 in words is "twenty-one million, seven hundred forty-two thousand, one hundred thirty-eight".