21214981 has 2 divisors, whose sum is σ = 21214982. Its totient is φ = 21214980.

The previous prime is 21214961. The next prime is 21215009. The reversal of 21214981 is 18941212.

It is an a-pointer prime, because the next prime (21215009) can be obtained adding 21214981 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14630625 + 6584356 = 3825^2 + 2566^2 .

It is a cyclic number.

It is not a de Polignac number, because 21214981 - 2¹⁹ = 20690693 is a prime.

It is a super-2 number, since 2×21214981² = 900150837660722, which contains 22 as substring.

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

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21214931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607490 + 10607491.

It is an arithmetic number, because the mean of its divisors is an integer number (10607491).

Almost surely, 2^21214981 is an apocalyptic number.

It is an amenable number.

21214981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21214981 is an equidigital number, since it uses as much as digits as its factorization.

21214981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 28.

The square root of 21214981 is about 4605.9723186315. The cubic root of 21214981 is about 276.8306775796.

The spelling of 21214981 in words is "twenty-one million, two hundred fourteen thousand, nine hundred eighty-one".