21501161 has 16 divisors (see below), whose sum is σ = 24254208. Its totient is φ = 18891600.

The previous prime is 21501131. The next prime is 21501187. The reversal of 21501161 is 16110512.

It is a cyclic number.

It is not a de Polignac number, because 21501161 - 2¹⁰ = 21500137 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21501101) 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, 61790 + ... + 62136.

It is an arithmetic number, because the mean of its divisors is an integer number (1515888).

Almost surely, 2^21501161 is an apocalyptic number.

It is an amenable number.

21501161 is a deficient number, since it is larger than the sum of its proper divisors (2753047).

21501161 is a wasteful number, since it uses less digits than its factorization.

21501161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532.

The product of its (nonzero) digits is 60, while the sum is 17.

The square root of 21501161 is about 4636.9344399075. The cubic root of 21501161 is about 278.0698934040.

Adding to 21501161 its reverse (16110512), we get a palindrome (37611673).

The spelling of 21501161 in words is "twenty-one million, five hundred one thousand, one hundred sixty-one".