21712051 has 4 divisors (see below), whose sum is σ = 21735472. Its totient is φ = 21688632.

The previous prime is 21711973. The next prime is 21712057. The reversal of 21712051 is 15021712.

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-21712051 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21712057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10260 + ... + 12193.

It is an arithmetic number, because the mean of its divisors is an integer number (5433868).

Almost surely, 2^21712051 is an apocalyptic number.

21712051 is a deficient number, since it is larger than the sum of its proper divisors (23421).

21712051 is an equidigital number, since it uses as much as digits as its factorization.

21712051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23420.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21712051 is about 4659.6191904489. The cubic root of 21712051 is about 278.9760688269.

Adding to 21712051 its reverse (15021712), we get a palindrome (36733763).

The spelling of 21712051 in words is "twenty-one million, seven hundred twelve thousand, fifty-one".