20551666 has 4 divisors (see below), whose sum is σ = 30827502. Its totient is φ = 10275832.

The previous prime is 20551637. The next prime is 20551697. The reversal of 20551666 is 66615502.

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., 20439441 + 112225 = 4521^2 + 335^2 .

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 an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5137915 + ... + 5137918.

Almost surely, 2^20551666 is an apocalyptic number.

20551666 is a deficient number, since it is larger than the sum of its proper divisors (10275836).

20551666 is a wasteful number, since it uses less digits than its factorization.

20551666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10275835.

The product of its (nonzero) digits is 10800, while the sum is 31.

The square root of 20551666 is about 4533.3945339006. The cubic root of 20551666 is about 273.9149131081.

It can be divided in two parts, 2055 and 1666, that added together give a square (3721 = 61²).

The spelling of 20551666 in words is "twenty million, five hundred fifty-one thousand, six hundred sixty-six".