21651001 has 4 divisors (see below), whose sum is σ = 21760000. Its totient is φ = 21542004.

The previous prime is 21650999. The next prime is 21651011. The reversal of 21651001 is 10015612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21651001 - 2¹ = 21650999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21651011) 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, 54201 + ... + 54598.

It is an arithmetic number, because the mean of its divisors is an integer number (5440000).

Almost surely, 2^21651001 is an apocalyptic number.

It is an amenable number.

21651001 is a deficient number, since it is larger than the sum of its proper divisors (108999).

21651001 is a wasteful number, since it uses less digits than its factorization.

21651001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108998.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 21651001 is about 4653.0636144373. The cubic root of 21651001 is about 278.7143481655.

Adding to 21651001 its reverse (10015612), we get a palindrome (31666613).

The spelling of 21651001 in words is "twenty-one million, six hundred fifty-one thousand, one".