21132401 has 4 divisors (see below), whose sum is σ = 21223332. Its totient is φ = 21041472.

The previous prime is 21132383. The next prime is 21132481. The reversal of 21132401 is 10423112.

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 12952801 + 8179600 = 3599^2 + 2860^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21132401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21132481) 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, 45116 + ... + 45581.

It is an arithmetic number, because the mean of its divisors is an integer number (5305833).

Almost surely, 2^21132401 is an apocalyptic number.

It is an amenable number.

21132401 is a deficient number, since it is larger than the sum of its proper divisors (90931).

21132401 is an equidigital number, since it uses as much as digits as its factorization.

21132401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90930.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21132401 is about 4596.9991298672. Note that the first 3 decimals coincide. The cubic root of 21132401 is about 276.4710197252.

Adding to 21132401 its reverse (10423112), we get a palindrome (31555513).

The spelling of 21132401 in words is "twenty-one million, one hundred thirty-two thousand, four hundred one".