21997772 has 6 divisors (see below), whose sum is σ = 38496108. Its totient is φ = 10998884.

The previous prime is 21997753. The next prime is 21997777. The reversal of 21997772 is 27779912.

It is not an unprimeable number, because it can be changed into a prime (21997777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2749718 + ... + 2749725.

It is an arithmetic number, because the mean of its divisors is an integer number (6416018).

Almost surely, 2^21997772 is an apocalyptic number.

It is an amenable number.

21997772 is a deficient number, since it is larger than the sum of its proper divisors (16498336).

21997772 is a wasteful number, since it uses less digits than its factorization.

21997772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5499447 (or 5499445 counting only the distinct ones).

The product of its digits is 111132, while the sum is 44.

The square root of 21997772 is about 4690.1782482119. The cubic root of 21997772 is about 280.1944737407.

The spelling of 21997772 in words is "twenty-one million, nine hundred ninety-seven thousand, seven hundred seventy-two".