661212381 has 16 divisors (see below), whose sum is σ = 893249280. Its totient is φ = 435025920.

The previous prime is 661212379. The next prime is 661212397. The reversal of 661212381 is 183212166.

It is not a de Polignac number, because 661212381 - 2¹ = 661212379 is a prime.

It is a super-2 number, since 2×661212381² = 874403625575378322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661212301) 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 in 15 ways as a sum of consecutive naturals, for example, 76941 + ... + 85101.

It is an arithmetic number, because the mean of its divisors is an integer number (55828080).

Almost surely, 2^661212381 is an apocalyptic number.

It is an amenable number.

661212381 is a deficient number, since it is larger than the sum of its proper divisors (232036899).

661212381 is a wasteful number, since it uses less digits than its factorization.

661212381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8516.

The product of its digits is 3456, while the sum is 30.

The square root of 661212381 is about 25714.0502643983. The cubic root of 661212381 is about 871.1915592527.

The spelling of 661212381 in words is "six hundred sixty-one million, two hundred twelve thousand, three hundred eighty-one".