21917684 has 6 divisors (see below), whose sum is σ = 38355954. Its totient is φ = 10958840.

The previous prime is 21917683. The next prime is 21917699. The reversal of 21917684 is 48671912.

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 3341584 = 4310^2 + 1828^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2739707 + ... + 2739714.

It is an arithmetic number, because the mean of its divisors is an integer number (6392659).

Almost surely, 2^21917684 is an apocalyptic number.

It is an amenable number.

21917684 is a deficient number, since it is larger than the sum of its proper divisors (16438270).

21917684 is a wasteful number, since it uses less digits than its factorization.

21917684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5479425 (or 5479423 counting only the distinct ones).

The product of its digits is 24192, while the sum is 38.

The square root of 21917684 is about 4681.6326212124. The cubic root of 21917684 is about 279.8540225476.

The spelling of 21917684 in words is "twenty-one million, nine hundred seventeen thousand, six hundred eighty-four".