21299691 has 16 divisors (see below), whose sum is σ = 34366464. Its totient is φ = 11455104.

The previous prime is 21299687. The next prime is 21299701. The reversal of 21299691 is 19699212.

It is not a de Polignac number, because 21299691 - 2² = 21299687 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21299611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29475 + ... + 30188.

It is an arithmetic number, because the mean of its divisors is an integer number (2147904).

Almost surely, 2^21299691 is an apocalyptic number.

21299691 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21299691 is a deficient number, since it is larger than the sum of its proper divisors (13066773).

21299691 is a wasteful number, since it uses less digits than its factorization.

21299691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59690.

The product of its digits is 17496, while the sum is 39.

The square root of 21299691 is about 4615.1588271694. The cubic root of 21299691 is about 277.1986437178.

The spelling of 21299691 in words is "twenty-one million, two hundred ninety-nine thousand, six hundred ninety-one".