21439457 has 8 divisors (see below), whose sum is σ = 23174760. Its totient is φ = 19716480.

The previous prime is 21439441. The next prime is 21439459. The reversal of 21439457 is 75493412.

It can be written as a sum of positive squares in 4 ways, for example, as 58081 + 21381376 = 241^2 + 4624^2 .

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 21439457 - 2⁴ = 21439441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21439459) 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, 719 + ... + 6587.

It is an arithmetic number, because the mean of its divisors is an integer number (2896845).

Almost surely, 2^21439457 is an apocalyptic number.

It is an amenable number.

21439457 is a deficient number, since it is larger than the sum of its proper divisors (1735303).

21439457 is a wasteful number, since it uses less digits than its factorization.

21439457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6163.

The product of its digits is 30240, while the sum is 35.

The square root of 21439457 is about 4630.2761256754. The cubic root of 21439457 is about 277.8036370178.

The spelling of 21439457 in words is "twenty-one million, four hundred thirty-nine thousand, four hundred fifty-seven".