263661981 has 8 divisors (see below), whose sum is σ = 383508384. Its totient is φ = 159795120.

The previous prime is 263661977. The next prime is 263661989. The reversal of 263661981 is 189166362.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 263661981 - 2² = 263661977 is a prime.

It is a super-4 number, since 4×263661981⁴ (a number of 35 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (263661989) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3994846 + ... + 3994911.

It is an arithmetic number, because the mean of its divisors is an integer number (47938548).

Almost surely, 2^263661981 is an apocalyptic number.

It is an amenable number.

263661981 is a deficient number, since it is larger than the sum of its proper divisors (119846403).

263661981 is a wasteful number, since it uses less digits than its factorization.

263661981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7989771.

The product of its digits is 93312, while the sum is 42.

The square root of 263661981 is about 16237.6716619102. The cubic root of 263661981 is about 641.2329592803.

The spelling of 263661981 in words is "two hundred sixty-three million, six hundred sixty-one thousand, nine hundred eighty-one".