21409799 has 4 divisors (see below), whose sum is σ = 21485736. Its totient is φ = 21333864.

The previous prime is 21409793. The next prime is 21409807. The reversal of 21409799 is 99790412.

It is a happy number.

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 21409799 - 2⁸ = 21409543 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21409793) 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, 37544 + ... + 38109.

It is an arithmetic number, because the mean of its divisors is an integer number (5371434).

Almost surely, 2^21409799 is an apocalyptic number.

21409799 is a deficient number, since it is larger than the sum of its proper divisors (75937).

21409799 is an equidigital number, since it uses as much as digits as its factorization.

21409799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75936.

The product of its (nonzero) digits is 40824, while the sum is 41.

The square root of 21409799 is about 4627.0724005574. The cubic root of 21409799 is about 277.6754791958.

The spelling of 21409799 in words is "twenty-one million, four hundred nine thousand, seven hundred ninety-nine".