21072961 has 8 divisors (see below), whose sum is σ = 25936064. Its totient is φ = 16673040.

The previous prime is 21072923. The next prime is 21072973. The reversal of 21072961 is 16927012.

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 21072961 - 2⁷ = 21072833 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (21072361) 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, 115695 + ... + 115876.

It is an arithmetic number, because the mean of its divisors is an integer number (3242008).

Almost surely, 2^21072961 is an apocalyptic number.

It is an amenable number.

21072961 is a deficient number, since it is larger than the sum of its proper divisors (4863103).

21072961 is a wasteful number, since it uses less digits than its factorization.

21072961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231591.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21072961 is about 4590.5294901569. The cubic root of 21072961 is about 276.2115623922.

Adding to 21072961 its reverse (16927012), we get a palindrome (37999973).

The spelling of 21072961 in words is "twenty-one million, seventy-two thousand, nine hundred sixty-one".