21605151 has 16 divisors (see below), whose sum is σ = 30096000. Its totient is φ = 13772448.

The previous prime is 21605123. The next prime is 21605159. The reversal of 21605151 is 15150612.

It is not a de Polignac number, because 21605151 - 2¹³ = 21596959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605159) 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, 4900 + ... + 8198.

It is an arithmetic number, because the mean of its divisors is an integer number (1881000).

Almost surely, 2^21605151 is an apocalyptic number.

21605151 is a deficient number, since it is larger than the sum of its proper divisors (8490849).

21605151 is a wasteful number, since it uses less digits than its factorization.

21605151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3398.

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 21605151 is about 4648.1341417821. The cubic root of 21605151 is about 278.5174660573.

Adding to 21605151 its product of nonzero digits (300), we get a triangular number (21605451 = T₆₅₇₃).

Adding to 21605151 its reverse (15150612), we get a palindrome (36755763).

The spelling of 21605151 in words is "twenty-one million, six hundred five thousand, one hundred fifty-one".