21210061 has 4 divisors (see below), whose sum is σ = 22326400. Its totient is φ = 20093724.

The previous prime is 21210053. The next prime is 21210089. The reversal of 21210061 is 16001212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21210061 - 2³ = 21210053 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 (21210011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 558141 + ... + 558178.

It is an arithmetic number, because the mean of its divisors is an integer number (5581600).

Almost surely, 2^21210061 is an apocalyptic number.

It is an amenable number.

21210061 is a deficient number, since it is larger than the sum of its proper divisors (1116339).

21210061 is a wasteful number, since it uses less digits than its factorization.

21210061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1116338.

The product of its (nonzero) digits is 24, while the sum is 13.

The square root of 21210061 is about 4605.4381984780. The cubic root of 21210061 is about 276.8092758441.

Adding to 21210061 its reverse (16001212), we get a palindrome (37211273).

The spelling of 21210061 in words is "twenty-one million, two hundred ten thousand, sixty-one".