1221571381 has 2 divisors, whose sum is σ = 1221571382. Its totient is φ = 1221571380.

The previous prime is 1221571367. The next prime is 1221571387. The reversal of 1221571381 is 1831751221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 972878481 + 248692900 = 31191^2 + 15770^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221571381 - 2¹¹ = 1221569333 is a prime.

It is a super-2 number, since 2×1221571381² = 2984473277756494322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221571387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610785690 + 610785691.

It is an arithmetic number, because the mean of its divisors is an integer number (610785691).

Almost surely, 2^1221571381 is an apocalyptic number.

It is an amenable number.

1221571381 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221571381 is an equidigital number, since it uses as much as digits as its factorization.

1221571381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3360, while the sum is 31.

The square root of 1221571381 is about 34950.9854081398. The cubic root of 1221571381 is about 1068.9882948872.

The spelling of 1221571381 in words is "one billion, two hundred twenty-one million, five hundred seventy-one thousand, three hundred eighty-one".