20742178 has 4 divisors (see below), whose sum is σ = 31113270. Its totient is φ = 10371088.

The previous prime is 20742151. The next prime is 20742179. The reversal of 20742178 is 87124702.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20007729 + 734449 = 4473^2 + 857^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (20742179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5185543 + ... + 5185546.

Almost surely, 2^20742178 is an apocalyptic number.

20742178 is a deficient number, since it is larger than the sum of its proper divisors (10371092).

20742178 is a wasteful number, since it uses less digits than its factorization.

20742178 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10371091.

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 20742178 is about 4554.3581326022. The cubic root of 20742178 is about 274.7586996263.

The spelling of 20742178 in words is "twenty million, seven hundred forty-two thousand, one hundred seventy-eight".