21660451 has 4 divisors (see below), whose sum is σ = 21780304. Its totient is φ = 21540600.

The previous prime is 21660449. The next prime is 21660461. The reversal of 21660451 is 15406612.

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 21660451 - 2¹ = 21660449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660421) 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, 59655 + ... + 60016.

It is an arithmetic number, because the mean of its divisors is an integer number (5445076).

Almost surely, 2^21660451 is an apocalyptic number.

21660451 is a deficient number, since it is larger than the sum of its proper divisors (119853).

21660451 is a wasteful number, since it uses less digits than its factorization.

21660451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119852.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21660451 is about 4654.0789636619. The cubic root of 21660451 is about 278.7548923645.

The spelling of 21660451 in words is "twenty-one million, six hundred sixty thousand, four hundred fifty-one".