21091072 has 18 divisors (see below), whose sum is σ = 42100268. Its totient is φ = 10545408.

The previous prime is 21091051. The next prime is 21091079. The reversal of 21091072 is 27019012.

It is not an unprimeable number, because it can be changed into a prime (21091079) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40938 + ... + 41449.

Almost surely, 2^21091072 is an apocalyptic number.

It is an amenable number.

21091072 is a deficient number, since it is larger than the sum of its proper divisors (21009196).

21091072 is an frugal number, since it uses more digits than its factorization.

21091072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82403 (or 82389 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 22.

The square root of 21091072 is about 4592.5017147520. The cubic root of 21091072 is about 276.2906690601.

The spelling of 21091072 in words is "twenty-one million, ninety-one thousand, seventy-two".