21343661 has 2 divisors, whose sum is σ = 21343662. Its totient is φ = 21343660.

The previous prime is 21343649. The next prime is 21343691. The reversal of 21343661 is 16634312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19669225 + 1674436 = 4435^2 + 1294^2 .

It is a cyclic number.

It is not a de Polignac number, because 21343661 - 2¹⁸ = 21081517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21343661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21343601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10671830 + 10671831.

It is an arithmetic number, because the mean of its divisors is an integer number (10671831).

Almost surely, 2^21343661 is an apocalyptic number.

It is an amenable number.

21343661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21343661 is an equidigital number, since it uses as much as digits as its factorization.

21343661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 26.

The square root of 21343661 is about 4619.9200209527. The cubic root of 21343661 is about 277.3892575458.

Adding to 21343661 its reverse (16634312), we get a palindrome (37977973).

The spelling of 21343661 in words is "twenty-one million, three hundred forty-three thousand, six hundred sixty-one".