201821661279 has 12 divisors (see below), whose sum is σ = 333165917136. Its totient is φ = 115326663552.

The previous prime is 201821661229. The next prime is 201821661311. The reversal of 201821661279 is 972166128102.

201821661279 is a `hidden beast` number, since 2 + 0 + 1 + 8 + 21 + 6 + 612 + 7 + 9 = 666.

It is not a de Polignac number, because 201821661279 - 2⁸ = 201821661023 is a prime.

It is a super-2 number, since 2×201821661279² (a number of 23 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (201821661229) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1601759154 + ... + 1601759279.

It is an arithmetic number, because the mean of its divisors is an integer number (27763826428).

Almost surely, 2^201821661279 is an apocalyptic number.

201821661279 is a deficient number, since it is larger than the sum of its proper divisors (131344255857).

201821661279 is a wasteful number, since it uses less digits than its factorization.

201821661279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3203518446 (or 3203518443 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 201821661279 in words is "two hundred one billion, eight hundred twenty-one million, six hundred sixty-one thousand, two hundred seventy-nine".