21776261 has 16 divisors (see below), whose sum is σ = 24911040. Its totient is φ = 18869760.

The previous prime is 21776243. The next prime is 21776263. The reversal of 21776261 is 16267712.

It is not a de Polignac number, because 21776261 - 2¹⁸ = 21514117 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 (21776263) 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 15 ways as a sum of consecutive naturals, for example, 32021 + ... + 32693.

It is an arithmetic number, because the mean of its divisors is an integer number (1556940).

Almost surely, 2^21776261 is an apocalyptic number.

It is an amenable number.

21776261 is a deficient number, since it is larger than the sum of its proper divisors (3134779).

21776261 is a wasteful number, since it uses less digits than its factorization.

21776261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 836.

The product of its digits is 7056, while the sum is 32.

The square root of 21776261 is about 4666.5041519322. The cubic root of 21776261 is about 279.2508075573.

The spelling of 21776261 in words is "twenty-one million, seven hundred seventy-six thousand, two hundred sixty-one".