21721082 has 4 divisors (see below), whose sum is σ = 32581626. Its totient is φ = 10860540.

The previous prime is 21721081. The next prime is 21721127. The reversal of 21721082 is 28012712.

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., 20620681 + 1100401 = 4541^2 + 1049^2 .

It is not an unprimeable number, because it can be changed into a prime (21721081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5430269 + ... + 5430272.

Almost surely, 2^21721082 is an apocalyptic number.

21721082 is a deficient number, since it is larger than the sum of its proper divisors (10860544).

21721082 is a wasteful number, since it uses less digits than its factorization.

21721082 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10860543.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21721082 is about 4660.5881603077. The cubic root of 21721082 is about 279.0147429507.

Adding to 21721082 its reverse (28012712), we get a palindrome (49733794).

The spelling of 21721082 in words is "twenty-one million, seven hundred twenty-one thousand, eighty-two".