21346561 has 4 divisors (see below), whose sum is σ = 21586500. Its totient is φ = 21106624.

The previous prime is 21346547. The next prime is 21346571. The reversal of 21346561 is 16564312.

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 12531600 + 8814961 = 3540^2 + 2969^2 .

It is a cyclic number.

It is not a de Polignac number, because 21346561 - 2¹¹ = 21344513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21346571) 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, 119836 + ... + 120013.

It is an arithmetic number, because the mean of its divisors is an integer number (5396625).

Almost surely, 2^21346561 is an apocalyptic number.

It is an amenable number.

21346561 is a deficient number, since it is larger than the sum of its proper divisors (239939).

21346561 is an equidigital number, since it uses as much as digits as its factorization.

21346561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239938.

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

The square root of 21346561 is about 4620.2338685396. The cubic root of 21346561 is about 277.4018200957.

The spelling of 21346561 in words is "twenty-one million, three hundred forty-six thousand, five hundred sixty-one".