21052981 has 8 divisors (see below), whose sum is σ = 22271040. Its totient is φ = 19860192.

The previous prime is 21052979. The next prime is 21053009. The reversal of 21052981 is 18925012.

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 21052981 - 2¹ = 21052979 is a prime.

It is a super-2 number, since 2×21052981² = 886456017972722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21052081) 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, 4591 + ... + 7948.

It is an arithmetic number, because the mean of its divisors is an integer number (2783880).

Almost surely, 2^21052981 is an apocalyptic number.

It is an amenable number.

21052981 is a deficient number, since it is larger than the sum of its proper divisors (1218059).

21052981 is a wasteful number, since it uses less digits than its factorization.

21052981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12635.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 21052981 is about 4588.3527545297. The cubic root of 21052981 is about 276.1242395571.

Adding to 21052981 its reverse (18925012), we get a palindrome (39977993).

The spelling of 21052981 in words is "twenty-one million, fifty-two thousand, nine hundred eighty-one".