21043739 has 4 divisors (see below), whose sum is σ = 22281624. Its totient is φ = 19805856.

The previous prime is 21043691. The next prime is 21043747. The reversal of 21043739 is 93734012.

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 21043739 - 2⁸ = 21043483 is a prime.

It is a super-2 number, since 2×21043739² = 885677902200242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21043339) 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, 618917 + ... + 618950.

It is an arithmetic number, because the mean of its divisors is an integer number (5570406).

Almost surely, 2^21043739 is an apocalyptic number.

21043739 is a deficient number, since it is larger than the sum of its proper divisors (1237885).

21043739 is a wasteful number, since it uses less digits than its factorization.

21043739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1237884.

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 21043739 is about 4587.3455287345. The cubic root of 21043739 is about 276.0838285937.

The spelling of 21043739 in words is "twenty-one million, forty-three thousand, seven hundred thirty-nine".