21354661 has 4 divisors (see below), whose sum is σ = 21931852. Its totient is φ = 20777472.

The previous prime is 21354659. The next prime is 21354667. The reversal of 21354661 is 16645312.

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 15444900 + 5909761 = 3930^2 + 2431^2 .

It is a cyclic number.

It is not a de Polignac number, because 21354661 - 2¹ = 21354659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21354667) 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, 288540 + ... + 288613.

It is an arithmetic number, because the mean of its divisors is an integer number (5482963).

Almost surely, 2^21354661 is an apocalyptic number.

It is an amenable number.

21354661 is a deficient number, since it is larger than the sum of its proper divisors (577191).

21354661 is an equidigital number, since it uses as much as digits as its factorization.

21354661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 577190.

The product of its digits is 4320, while the sum is 28.

The square root of 21354661 is about 4621.1103644038. The cubic root of 21354661 is about 277.4369025710.

Adding to 21354661 its reverse (16645312), we get a palindrome (37999973).

The spelling of 21354661 in words is "twenty-one million, three hundred fifty-four thousand, six hundred sixty-one".