21406739 has 8 divisors (see below), whose sum is σ = 21880320. Its totient is φ = 20938176.

The previous prime is 21406729. The next prime is 21406747. The reversal of 21406739 is 93760412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21406739 - 2²⁴ = 4629523 is a prime.

It is a super-2 number, since 2×21406739² = 916496949228242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21406729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8117 + ... + 10425.

It is an arithmetic number, because the mean of its divisors is an integer number (2735040).

Almost surely, 2^21406739 is an apocalyptic number.

21406739 is a deficient number, since it is larger than the sum of its proper divisors (473581).

21406739 is a wasteful number, since it uses less digits than its factorization.

21406739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2509.

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 21406739 is about 4626.7417260962. The cubic root of 21406739 is about 277.6622496235.

The spelling of 21406739 in words is "twenty-one million, four hundred six thousand, seven hundred thirty-nine".