21196921 has 4 divisors (see below), whose sum is σ = 21236644. Its totient is φ = 21157200.

The previous prime is 21196919. The next prime is 21196933. The reversal of 21196921 is 12969112.

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 14100025 + 7096896 = 3755^2 + 2664^2 .

It is a cyclic number.

It is not a de Polignac number, because 21196921 - 2¹ = 21196919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21196621) 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, 19050 + ... + 20131.

It is an arithmetic number, because the mean of its divisors is an integer number (5309161).

Almost surely, 2^21196921 is an apocalyptic number.

It is an amenable number.

21196921 is a deficient number, since it is larger than the sum of its proper divisors (39723).

21196921 is an equidigital number, since it uses as much as digits as its factorization.

21196921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39722.

The product of its digits is 1944, while the sum is 31.

The square root of 21196921 is about 4604.0114031136. The cubic root of 21196921 is about 276.7521013227.

The spelling of 21196921 in words is "twenty-one million, one hundred ninety-six thousand, nine hundred twenty-one".