1212385781 has 4 divisors (see below), whose sum is σ = 1216259532. Its totient is φ = 1208512032.

The previous prime is 1212385739. The next prime is 1212385813. The reversal of 1212385781 is 1875832121.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 598585156 + 613800625 = 24466^2 + 24775^2 .

It is a cyclic number.

It is not a de Polignac number, because 1212385781 - 2¹⁴ = 1212369397 is a prime.

It is a super-2 number, since 2×1212385781² = 2939758563941959922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1212385381) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1936406 + ... + 1937031.

It is an arithmetic number, because the mean of its divisors is an integer number (304064883).

Almost surely, 2^1212385781 is an apocalyptic number.

It is an amenable number.

1212385781 is a deficient number, since it is larger than the sum of its proper divisors (3873751).

1212385781 is an equidigital number, since it uses as much as digits as its factorization.

1212385781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3873750.

The product of its digits is 26880, while the sum is 38.

The square root of 1212385781 is about 34819.3305650755. The cubic root of 1212385781 is about 1066.3021333234.

The spelling of 1212385781 in words is "one billion, two hundred twelve million, three hundred eighty-five thousand, seven hundred eighty-one".