21404737 has 4 divisors (see below), whose sum is σ = 21414960. Its totient is φ = 21394516.

The previous prime is 21404731. The next prime is 21404741. The reversal of 21404737 is 73740412.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21404737 - 2³ = 21404729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21404731) 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, 703 + ... + 6580.

It is an arithmetic number, because the mean of its divisors is an integer number (5353740).

Almost surely, 2^21404737 is an apocalyptic number.

It is an amenable number.

21404737 is a deficient number, since it is larger than the sum of its proper divisors (10223).

21404737 is an equidigital number, since it uses as much as digits as its factorization.

21404737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10222.

The product of its (nonzero) digits is 4704, while the sum is 28.

The square root of 21404737 is about 4626.5253700807. The cubic root of 21404737 is about 277.6535935152.

The spelling of 21404737 in words is "twenty-one million, four hundred four thousand, seven hundred thirty-seven".