21681011 has 8 divisors (see below), whose sum is σ = 23937984. Its totient is φ = 19471720.

The previous prime is 21681007. The next prime is 21681029. The reversal of 21681011 is 11018612.

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 21681011 - 2² = 21681007 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21681031) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10961 + ... + 12786.

It is an arithmetic number, because the mean of its divisors is an integer number (2992248).

Almost surely, 2^21681011 is an apocalyptic number.

21681011 is a deficient number, since it is larger than the sum of its proper divisors (2256973).

21681011 is a wasteful number, since it uses less digits than its factorization.

21681011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23841.

The product of its (nonzero) digits is 96, while the sum is 20.

The square root of 21681011 is about 4656.2872548845. The cubic root of 21681011 is about 278.8430620922.

Adding to 21681011 its reverse (11018612), we get a palindrome (32699623).

The spelling of 21681011 in words is "twenty-one million, six hundred eighty-one thousand, eleven".