21370981 has 2 divisors, whose sum is σ = 21370982. Its totient is φ = 21370980.

The previous prime is 21370927. The next prime is 21371011. The reversal of 21370981 is 18907312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14822500 + 6548481 = 3850^2 + 2559^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21370981 is a prime.

It is a super-2 number, since 2×21370981² = 913437657804722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21370901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10685490 + 10685491.

It is an arithmetic number, because the mean of its divisors is an integer number (10685491).

Almost surely, 2^21370981 is an apocalyptic number.

It is an amenable number.

21370981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21370981 is an equidigital number, since it uses as much as digits as its factorization.

21370981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21370981 is about 4622.8758365329. The cubic root of 21370981 is about 277.5075603275.

The spelling of 21370981 in words is "twenty-one million, three hundred seventy thousand, nine hundred eighty-one".