21651673 has 4 divisors (see below), whose sum is σ = 21866148. Its totient is φ = 21437200.

The previous prime is 21651667. The next prime is 21651683. The reversal of 21651673 is 37615612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 21418384 + 233289 = 4628^2 + 483^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21651673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21651683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107086 + ... + 107287.

It is an arithmetic number, because the mean of its divisors is an integer number (5466537).

Almost surely, 2^21651673 is an apocalyptic number.

It is an amenable number.

21651673 is a deficient number, since it is larger than the sum of its proper divisors (214475).

21651673 is a wasteful number, since it uses less digits than its factorization.

21651673 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214474.

The product of its digits is 7560, while the sum is 31.

The square root of 21651673 is about 4653.1358243662. The cubic root of 21651673 is about 278.7172316981.

The spelling of 21651673 in words is "twenty-one million, six hundred fifty-one thousand, six hundred seventy-three".