21957784 has 8 divisors (see below), whose sum is σ = 41170860. Its totient is φ = 10978888.

The previous prime is 21957781. The next prime is 21957799. The reversal of 21957784 is 48775912.

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21957784.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21957781) 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, 1372354 + ... + 1372369.

Almost surely, 2^21957784 is an apocalyptic number.

It is an amenable number.

21957784 is a deficient number, since it is larger than the sum of its proper divisors (19213076).

21957784 is a wasteful number, since it uses less digits than its factorization.

21957784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2744729 (or 2744725 counting only the distinct ones).

The product of its digits is 141120, while the sum is 43.

The square root of 21957784 is about 4685.9133581405. The cubic root of 21957784 is about 280.0245896772.

The spelling of 21957784 in words is "twenty-one million, nine hundred fifty-seven thousand, seven hundred eighty-four".