21580651 has 4 divisors (see below), whose sum is σ = 21738312. Its totient is φ = 21422992.

The previous prime is 21580613. The next prime is 21580673. The reversal of 21580651 is 15608512.

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

It is a cyclic number.

It is not a de Polignac number, because 21580651 - 2¹⁹ = 21056363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21580051) 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, 78625 + ... + 78898.

It is an arithmetic number, because the mean of its divisors is an integer number (5434578).

Almost surely, 2^21580651 is an apocalyptic number.

21580651 is a deficient number, since it is larger than the sum of its proper divisors (157661).

21580651 is a wasteful number, since it uses less digits than its factorization.

21580651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157660.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21580651 is about 4645.4979281020. The cubic root of 21580651 is about 278.4121476718.

The spelling of 21580651 in words is "twenty-one million, five hundred eighty thousand, six hundred fifty-one".