21084681 has 16 divisors (see below), whose sum is σ = 29196288. Its totient is φ = 13520400.

The previous prime is 21084677. The next prime is 21084683. The reversal of 21084681 is 18648012.

It is not a de Polignac number, because 21084681 - 2² = 21084677 is a prime.

It is a super-2 number, since 2×21084681² = 889127545743522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21084683) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17170 + ... + 18356.

It is an arithmetic number, because the mean of its divisors is an integer number (1824768).

Almost surely, 2^21084681 is an apocalyptic number.

It is an amenable number.

21084681 is a deficient number, since it is larger than the sum of its proper divisors (8111607).

21084681 is a wasteful number, since it uses less digits than its factorization.

21084681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1412.

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21084681 is about 4591.8058539098. The cubic root of 21084681 is about 276.2627591139.

The spelling of 21084681 in words is "twenty-one million, eighty-four thousand, six hundred eighty-one".