21148981 has 16 divisors (see below), whose sum is σ = 24796800. Its totient is φ = 17664768.

The previous prime is 21148979. The next prime is 21149021. The reversal of 21148981 is 18984112.

It is a cyclic number.

It is not a de Polignac number, because 21148981 - 2¹ = 21148979 is a prime.

It is a super-2 number, since 2×21148981² = 894558794676722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21148921) 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, 51505 + ... + 51913.

It is an arithmetic number, because the mean of its divisors is an integer number (1549800).

Almost surely, 2^21148981 is an apocalyptic number.

It is an amenable number.

21148981 is a deficient number, since it is larger than the sum of its proper divisors (3647819).

21148981 is an equidigital number, since it uses as much as digits as its factorization.

21148981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588.

The product of its digits is 4608, while the sum is 34.

The square root of 21148981 is about 4598.8021266412. The cubic root of 21148981 is about 276.5433051102.

The spelling of 21148981 in words is "twenty-one million, one hundred forty-eight thousand, nine hundred eighty-one".