21997550 has 24 divisors (see below), whose sum is σ = 41440800. Its totient is φ = 8686080.

The previous prime is 21997531. The next prime is 21997567. The reversal of 21997550 is 5579912.

It is a super-3 number, since 3×21997550³ (a number of 23 digits) contains 333 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 in 11 ways as a sum of consecutive naturals, for example, 1166 + ... + 6734.

It is an arithmetic number, because the mean of its divisors is an integer number (1726700).

Almost surely, 2^21997550 is an apocalyptic number.

21997550 is a deficient number, since it is larger than the sum of its proper divisors (19443250).

21997550 is a wasteful number, since it uses less digits than its factorization.

21997550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5660 (or 5655 counting only the distinct ones).

The product of its (nonzero) digits is 28350, while the sum is 38.

The square root of 21997550 is about 4690.1545816743. The cubic root of 21997550 is about 280.1935311698.

The spelling of 21997550 in words is "twenty-one million, nine hundred ninety-seven thousand, five hundred fifty".