261221961 has 64 divisors (see below), whose sum is σ = 480485376. Its totient is φ = 121824000.

The previous prime is 261221951. The next prime is 261222037. The reversal of 261221961 is 169122162.

It is not a de Polignac number, because 261221961 - 2⁵ = 261221929 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261221951) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 109936 + ... + 112286.

It is an arithmetic number, because the mean of its divisors is an integer number (7507584).

Almost surely, 2^261221961 is an apocalyptic number.

261221961 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

261221961 is a deficient number, since it is larger than the sum of its proper divisors (219263415).

261221961 is a wasteful number, since it uses less digits than its factorization.

261221961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2422.

The product of its digits is 2592, while the sum is 30.

The square root of 261221961 is about 16162.3624820136. The cubic root of 261221961 is about 639.2487612740.

It can be divided in two parts, 261 and 221961, that added together give a palindrome (222222).

The spelling of 261221961 in words is "two hundred sixty-one million, two hundred twenty-one thousand, nine hundred sixty-one".