21516913 has 8 divisors (see below), whose sum is σ = 23518656. Its totient is φ = 19522800.

The previous prime is 21516893. The next prime is 21516919. The reversal of 21516913 is 31961512.

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

It is not a de Polignac number, because 21516913 - 2²¹ = 19419761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21516919) 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, 5148 + ... + 8338.

It is an arithmetic number, because the mean of its divisors is an integer number (2939832).

Almost surely, 2^21516913 is an apocalyptic number.

It is an amenable number.

21516913 is a deficient number, since it is larger than the sum of its proper divisors (2001743).

21516913 is a wasteful number, since it uses less digits than its factorization.

21516913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3815.

The product of its digits is 1620, while the sum is 28.

The square root of 21516913 is about 4638.6326649132. The cubic root of 21516913 is about 278.1377825712.

The spelling of 21516913 in words is "twenty-one million, five hundred sixteen thousand, nine hundred thirteen".