21149681 has 12 divisors (see below), whose sum is σ = 24853248. Its totient is φ = 17630352.

The previous prime is 21149663. The next prime is 21149699. The reversal of 21149681 is 18694112.

It is an interprime number because it is at equal distance from previous prime (21149663) and next prime (21149699).

It is not a de Polignac number, because 21149681 - 2⁶ = 21149617 is a prime.

It is a super-2 number, since 2×21149681² = 894618012803522, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21149281) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8480 + ... + 10686.

It is an arithmetic number, because the mean of its divisors is an integer number (2071104).

Almost surely, 2^21149681 is an apocalyptic number.

It is an amenable number.

21149681 is a deficient number, since it is larger than the sum of its proper divisors (3703567).

21149681 is an equidigital number, since it uses as much as digits as its factorization.

21149681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2288 (or 2251 counting only the distinct ones).

The product of its digits is 3456, while the sum is 32.

The square root of 21149681 is about 4598.8782327868. The cubic root of 21149681 is about 276.5463561347.

The spelling of 21149681 in words is "twenty-one million, one hundred forty-nine thousand, six hundred eighty-one".