21516658 has 4 divisors (see below), whose sum is σ = 32274990. Its totient is φ = 10758328.

The previous prime is 21516653. The next prime is 21516659. The reversal of 21516658 is 85661512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 11675889 + 9840769 = 3417^2 + 3137^2 .

It is not an unprimeable number, because it can be changed into a prime (21516653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5379163 + ... + 5379166.

Almost surely, 2^21516658 is an apocalyptic number.

21516658 is a deficient number, since it is larger than the sum of its proper divisors (10758332).

21516658 is a wasteful number, since it uses less digits than its factorization.

21516658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10758331.

The product of its digits is 14400, while the sum is 34.

The square root of 21516658 is about 4638.6051782837. The cubic root of 21516658 is about 278.1366838167.

The spelling of 21516658 in words is "twenty-one million, five hundred sixteen thousand, six hundred fifty-eight".