21057739 has 8 divisors (see below), whose sum is σ = 21634560. Its totient is φ = 20486376.

The previous prime is 21057731. The next prime is 21057763. The reversal of 21057739 is 93775012.

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 21057739 - 2³ = 21057731 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21057731) 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, 7162 + ... + 9664.

It is an arithmetic number, because the mean of its divisors is an integer number (2704320).

Almost surely, 2^21057739 is an apocalyptic number.

21057739 is a deficient number, since it is larger than the sum of its proper divisors (576821).

21057739 is a wasteful number, since it uses less digits than its factorization.

21057739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2729.

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21057739 is about 4588.8712119649. The cubic root of 21057739 is about 276.1450394646.

The spelling of 21057739 in words is "twenty-one million, fifty-seven thousand, seven hundred thirty-nine".