21617051 has 4 divisors (see below), whose sum is σ = 21787392. Its totient is φ = 21446712.

The previous prime is 21617027. The next prime is 21617053. The reversal of 21617051 is 15071612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21617051 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21617053) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 84980 + ... + 85233.

It is an arithmetic number, because the mean of its divisors is an integer number (5446848).

Almost surely, 2^21617051 is an apocalyptic number.

21617051 is a deficient number, since it is larger than the sum of its proper divisors (170341).

21617051 is a wasteful number, since it uses less digits than its factorization.

21617051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170340.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21617051 is about 4649.4140491034. The cubic root of 21617051 is about 278.5685919751.

Adding to 21617051 its reverse (15071612), we get a palindrome (36688663).

The spelling of 21617051 in words is "twenty-one million, six hundred seventeen thousand, fifty-one".