213536781 has 6 divisors (see below), whose sum is σ = 308442030. Its totient is φ = 142357848.

The previous prime is 213536749. The next prime is 213536789. The reversal of 213536781 is 187635312.

213536781 is a `hidden beast` number, since 213 + 5 + 367 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 213452100 + 84681 = 14610^2 + 291^2 .

It is not a de Polignac number, because 213536781 - 2⁵ = 213536749 is a prime.

It is a super-2 number, since 2×213536781² = 91195913679683922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (213536789) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11863146 + ... + 11863163.

It is an arithmetic number, because the mean of its divisors is an integer number (51407005).

Almost surely, 2^213536781 is an apocalyptic number.

It is an amenable number.

213536781 is a deficient number, since it is larger than the sum of its proper divisors (94905249).

213536781 is a wasteful number, since it uses less digits than its factorization.

213536781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23726315 (or 23726312 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The square root of 213536781 is about 14612.8977619088. The cubic root of 213536781 is about 597.7105165545.

The spelling of 213536781 in words is "two hundred thirteen million, five hundred thirty-six thousand, seven hundred eighty-one".