21989897 has 4 divisors (see below), whose sum is σ = 23147280. Its totient is φ = 20832516.

The previous prime is 21989893. The next prime is 21989911. The reversal of 21989897 is 79898912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21989897 - 2² = 21989893 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21989893) 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 3 ways as a sum of consecutive naturals, for example, 578663 + ... + 578700.

It is an arithmetic number, because the mean of its divisors is an integer number (5786820).

Almost surely, 2^21989897 is an apocalyptic number.

It is an amenable number.

21989897 is a deficient number, since it is larger than the sum of its proper divisors (1157383).

21989897 is a wasteful number, since it uses less digits than its factorization.

21989897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1157382.

The product of its digits is 653184, while the sum is 53.

The square root of 21989897 is about 4689.3386527313. The cubic root of 21989897 is about 280.1610340687.

The spelling of 21989897 in words is "twenty-one million, nine hundred eighty-nine thousand, eight hundred ninety-seven".