21299497 has 4 divisors (see below), whose sum is σ = 21326020. Its totient is φ = 21272976.

The previous prime is 21299489. The next prime is 21299533. The reversal of 21299497 is 79499212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15968016 + 5331481 = 3996^2 + 2309^2 .

It is a cyclic number.

It is not a de Polignac number, because 21299497 - 2³ = 21299489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21299407) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12018 + ... + 13675.

It is an arithmetic number, because the mean of its divisors is an integer number (5331505).

Almost surely, 2^21299497 is an apocalyptic number.

It is an amenable number.

21299497 is a deficient number, since it is larger than the sum of its proper divisors (26523).

21299497 is an equidigital number, since it uses as much as digits as its factorization.

21299497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26522.

The product of its digits is 81648, while the sum is 43.

The square root of 21299497 is about 4615.1378094267. The cubic root of 21299497 is about 277.1978021297.

The spelling of 21299497 in words is "twenty-one million, two hundred ninety-nine thousand, four hundred ninety-seven".