21553966 has 8 divisors (see below), whose sum is σ = 36949680. Its totient is φ = 9237408.

The previous prime is 21553957. The next prime is 21553969. The reversal of 21553966 is 66935512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553969) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 769771 + ... + 769798.

It is an arithmetic number, because the mean of its divisors is an integer number (4618710).

Almost surely, 2^21553966 is an apocalyptic number.

21553966 is a deficient number, since it is larger than the sum of its proper divisors (15395714).

21553966 is a wasteful number, since it uses less digits than its factorization.

21553966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1539578.

The product of its digits is 48600, while the sum is 37.

The square root of 21553966 is about 4642.6249040817. The cubic root of 21553966 is about 278.2973458756.

The spelling of 21553966 in words is "twenty-one million, five hundred fifty-three thousand, nine hundred sixty-six".