21491066 has 4 divisors (see below), whose sum is σ = 32236602. Its totient is φ = 10745532.

The previous prime is 21491051. The next prime is 21491101. The reversal of 21491066 is 66019412.

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., 13845841 + 7645225 = 3721^2 + 2765^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5372765 + ... + 5372768.

Almost surely, 2^21491066 is an apocalyptic number.

21491066 is a deficient number, since it is larger than the sum of its proper divisors (10745536).

21491066 is a wasteful number, since it uses less digits than its factorization.

21491066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10745535.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21491066 is about 4635.8457696520. The cubic root of 21491066 is about 278.0263677697.

The spelling of 21491066 in words is "twenty-one million, four hundred ninety-one thousand, sixty-six".