21504057 has 8 divisors (see below), whose sum is σ = 29918784. Its totient is φ = 13712688.

The previous prime is 21504053. The next prime is 21504083. The reversal of 21504057 is 75040512.

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

It is not a de Polignac number, because 21504057 - 2² = 21504053 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21504053) 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, 155758 + ... + 155895.

It is an arithmetic number, because the mean of its divisors is an integer number (3739848).

Almost surely, 2^21504057 is an apocalyptic number.

It is an amenable number.

21504057 is a deficient number, since it is larger than the sum of its proper divisors (8414727).

21504057 is a wasteful number, since it uses less digits than its factorization.

21504057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311679.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21504057 is about 4637.2467046729. The cubic root of 21504057 is about 278.0823772920.

Adding to 21504057 its reverse (75040512), we get a palindrome (96544569).

The spelling of 21504057 in words is "twenty-one million, five hundred four thousand, fifty-seven".