21510061 has 4 divisors (see below), whose sum is σ = 22091452. Its totient is φ = 20928672.

The previous prime is 21510053. The next prime is 21510077. The reversal of 21510061 is 16001512.

It is a happy number.

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 15721225 + 5788836 = 3965^2 + 2406^2 .

It is a cyclic number.

It is not a de Polignac number, because 21510061 - 2³ = 21510053 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 (21510011) 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, 290640 + ... + 290713.

It is an arithmetic number, because the mean of its divisors is an integer number (5522863).

Almost surely, 2^21510061 is an apocalyptic number.

It is an amenable number.

21510061 is a deficient number, since it is larger than the sum of its proper divisors (581391).

21510061 is an equidigital number, since it uses as much as digits as its factorization.

21510061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 581390.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 21510061 is about 4637.8940263874. The cubic root of 21510061 is about 278.1082553737.

Adding to 21510061 its reverse (16001512), we get a palindrome (37511573).

The spelling of 21510061 in words is "twenty-one million, five hundred ten thousand, sixty-one".