21016261 has 8 divisors (see below), whose sum is σ = 25282880. Its totient is φ = 17065728.

The previous prime is 21016253. The next prime is 21016277. The reversal of 21016261 is 16261012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21016261 - 2³ = 21016253 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21016201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 78876 + ... + 79141.

It is an arithmetic number, because the mean of its divisors is an integer number (3160360).

Almost surely, 2^21016261 is an apocalyptic number.

It is an amenable number.

21016261 is a deficient number, since it is larger than the sum of its proper divisors (4266619).

21016261 is a wasteful number, since it uses less digits than its factorization.

21016261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158043.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21016261 is about 4584.3495721858. The cubic root of 21016261 is about 275.9636101642.

Adding to 21016261 its reverse (16261012), we get a palindrome (37277273).

It can be divided in two parts, 210 and 16261, that added together give a triangular number (16471 = T₁₈₁).

The spelling of 21016261 in words is "twenty-one million, sixteen thousand, two hundred sixty-one".