21761986 has 4 divisors (see below), whose sum is σ = 32642982. Its totient is φ = 10880992.

The previous prime is 21761983. The next prime is 21762007. The reversal of 21761986 is 68916712.

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., 21298225 + 463761 = 4615^2 + 681^2 .

It is a Smith number, since the sum of its digits (40) 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 (21761983) 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 as a sum of consecutive naturals, namely, 5440495 + ... + 5440498.

Almost surely, 2^21761986 is an apocalyptic number.

21761986 is a deficient number, since it is larger than the sum of its proper divisors (10880996).

21761986 is a wasteful number, since it uses less digits than its factorization.

21761986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10880995.

The product of its digits is 36288, while the sum is 40.

The square root of 21761986 is about 4664.9743836381. The cubic root of 21761986 is about 279.1897750926.

The spelling of 21761986 in words is "twenty-one million, seven hundred sixty-one thousand, nine hundred eighty-six".