21047961 has 8 divisors (see below), whose sum is σ = 30615264. Its totient is φ = 12756320.

The previous prime is 21047951. The next prime is 21047969. The reversal of 21047961 is 16974012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21047961 - 2⁷ = 21047833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21047969) 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, 318876 + ... + 318941.

It is an arithmetic number, because the mean of its divisors is an integer number (3826908).

Almost surely, 2^21047961 is an apocalyptic number.

It is an amenable number.

21047961 is a deficient number, since it is larger than the sum of its proper divisors (9567303).

21047961 is a wasteful number, since it uses less digits than its factorization.

21047961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 637831.

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 21047961 is about 4587.8056846384. The cubic root of 21047961 is about 276.1022909018.

The spelling of 21047961 in words is "twenty-one million, forty-seven thousand, nine hundred sixty-one".