21430661 has 4 divisors (see below), whose sum is σ = 24492192. Its totient is φ = 18369132.

The previous prime is 21430639. The next prime is 21430667. The reversal of 21430661 is 16603412.

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 21430661 - 2⁶ = 21430597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21430667) 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, 1530755 + ... + 1530768.

It is an arithmetic number, because the mean of its divisors is an integer number (6123048).

Almost surely, 2^21430661 is an apocalyptic number.

It is an amenable number.

21430661 is a deficient number, since it is larger than the sum of its proper divisors (3061531).

21430661 is an equidigital number, since it uses as much as digits as its factorization.

21430661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3061530.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21430661 is about 4629.3261928708. The cubic root of 21430661 is about 277.7656401748.

The spelling of 21430661 in words is "twenty-one million, four hundred thirty thousand, six hundred sixty-one".