21316761 has 18 divisors (see below), whose sum is σ = 31582590. Its totient is φ = 13854720.

The previous prime is 21316753. The next prime is 21316783. The reversal of 21316761 is 16761312.

It can be written as a sum of positive squares in 3 ways, for example, as 5035536 + 16281225 = 2244^2 + 4035^2 .

It is not a de Polignac number, because 21316761 - 2³ = 21316753 is a prime.

It is a super-2 number, since 2×21316761² = 908808599062242, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21316721) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 14425 + ... + 15833.

Almost surely, 2^21316761 is an apocalyptic number.

It is an amenable number.

21316761 is a deficient number, since it is larger than the sum of its proper divisors (10265829).

21316761 is a wasteful number, since it uses less digits than its factorization.

21316761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1497 (or 1453 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21316761 is about 4617.0077972644. The cubic root of 21316761 is about 277.2726747974.

The spelling of 21316761 in words is "twenty-one million, three hundred sixteen thousand, seven hundred sixty-one".