1263891821 has 2 divisors, whose sum is σ = 1263891822. Its totient is φ = 1263891820.

The previous prime is 1263891817. The next prime is 1263891841. The reversal of 1263891821 is 1281983621.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1191216196 + 72675625 = 34514^2 + 8525^2 .

It is an emirp because it is prime and its reverse (1281983621) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1263891821 - 2² = 1263891817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1263891841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 631945910 + 631945911.

It is an arithmetic number, because the mean of its divisors is an integer number (631945911).

Almost surely, 2^1263891821 is an apocalyptic number.

It is an amenable number.

1263891821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1263891821 is an equidigital number, since it uses as much as digits as its factorization.

1263891821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 41.

The square root of 1263891821 is about 35551.2562506587. The cubic root of 1263891821 is about 1081.1931888758.

The spelling of 1263891821 in words is "one billion, two hundred sixty-three million, eight hundred ninety-one thousand, eight hundred twenty-one".