1285001821 has 2 divisors, whose sum is σ = 1285001822. Its totient is φ = 1285001820.

The previous prime is 1285001791. The next prime is 1285001849. The reversal of 1285001821 is 1281005821.

It is an a-pointer prime, because the next prime (1285001849) can be obtained adding 1285001821 to its sum of digits (28).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 739078596 + 545923225 = 27186^2 + 23365^2 .

It is a cyclic number.

It is not a de Polignac number, because 1285001821 - 2¹⁷ = 1284870749 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1285001821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1285002821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 642500910 + 642500911.

It is an arithmetic number, because the mean of its divisors is an integer number (642500911).

Almost surely, 2^1285001821 is an apocalyptic number.

It is an amenable number.

1285001821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1285001821 is an equidigital number, since it uses as much as digits as its factorization.

1285001821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1280, while the sum is 28.

The square root of 1285001821 is about 35846.9220575491. The cubic root of 1285001821 is about 1087.1794825198.

It can be divided in two parts, 128500 and 1821, that added together give a 4-th power (130321 = 19⁴).

The spelling of 1285001821 in words is "one billion, two hundred eighty-five million, one thousand, eight hundred twenty-one".