21231641 has 4 divisors (see below), whose sum is σ = 21632292. Its totient is φ = 20830992.

The previous prime is 21231631. The next prime is 21231677. The reversal of 21231641 is 14613212.

21231641 = 394² + 395² + ... + 499².

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 5271616 + 15960025 = 2296^2 + 3995^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231641 - 2⁶ = 21231577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21231601) 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, 200246 + ... + 200351.

It is an arithmetic number, because the mean of its divisors is an integer number (5408073).

Almost surely, 2^21231641 is an apocalyptic number.

It is an amenable number.

21231641 is a deficient number, since it is larger than the sum of its proper divisors (400651).

21231641 is an equidigital number, since it uses as much as digits as its factorization.

21231641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400650.

The product of its digits is 288, while the sum is 20.

The square root of 21231641 is about 4607.7804852228. The cubic root of 21231641 is about 276.9031231211.

Adding to 21231641 its reverse (14613212), we get a palindrome (35844853).

It can be divided in two parts, 2123 and 1641, that multiplied together give a palindrome (3483843).

The spelling of 21231641 in words is "twenty-one million, two hundred thirty-one thousand, six hundred forty-one".