261921231 has 48 divisors (see below), whose sum is σ = 448654752. Its totient is φ = 145152000.

The previous prime is 261921221. The next prime is 261921239. The reversal of 261921231 is 132129162.

261921231 is a `hidden beast` number, since 2 + 619 + 2 + 12 + 31 = 666.

It is not a de Polignac number, because 261921231 - 2¹³ = 261913039 is a prime.

It is a super-2 number, since 2×261921231² = 137205462497110722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 261921195 and 261921204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261921239) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 144531 + ... + 146331.

It is an arithmetic number, because the mean of its divisors is an integer number (9346974).

Almost surely, 2^261921231 is an apocalyptic number.

261921231 is a deficient number, since it is larger than the sum of its proper divisors (186733521).

261921231 is a wasteful number, since it uses less digits than its factorization.

261921231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1944 (or 1941 counting only the distinct ones).

The product of its digits is 1296, while the sum is 27.

The square root of 261921231 is about 16183.9806907942. The cubic root of 261921231 is about 639.8186587463.

The spelling of 261921231 in words is "two hundred sixty-one million, nine hundred twenty-one thousand, two hundred thirty-one".