21516945 has 16 divisors (see below), whose sum is σ = 35538432. Its totient is φ = 11105280.

The previous prime is 21516919. The next prime is 21516947. The reversal of 21516945 is 54961512.

It is not a de Polignac number, because 21516945 - 2⁸ = 21516689 is a prime.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21516947) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22672 + ... + 23601.

It is an arithmetic number, because the mean of its divisors is an integer number (2221152).

Almost surely, 2^21516945 is an apocalyptic number.

It is an amenable number.

21516945 is a deficient number, since it is larger than the sum of its proper divisors (14021487).

21516945 is a wasteful number, since it uses less digits than its factorization.

21516945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46312.

The product of its digits is 10800, while the sum is 33.

The square root of 21516945 is about 4638.6361142043. The cubic root of 21516945 is about 278.1379204535.

The spelling of 21516945 in words is "twenty-one million, five hundred sixteen thousand, nine hundred forty-five".