21491716 has 6 divisors (see below), whose sum is σ = 37610510. Its totient is φ = 10745856.

The previous prime is 21491693. The next prime is 21491741. The reversal of 21491716 is 61719412.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 4186116 = 4160^2 + 2046^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2686461 + ... + 2686468.

Almost surely, 2^21491716 is an apocalyptic number.

It is an amenable number.

21491716 is a deficient number, since it is larger than the sum of its proper divisors (16118794).

21491716 is a wasteful number, since it uses less digits than its factorization.

21491716 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5372933 (or 5372931 counting only the distinct ones).

The product of its digits is 3024, while the sum is 31.

The square root of 21491716 is about 4635.9158749917. The cubic root of 21491716 is about 278.0291707223.

The spelling of 21491716 in words is "twenty-one million, four hundred ninety-one thousand, seven hundred sixteen".