21216057 has 8 divisors (see below), whose sum is σ = 28358880. Its totient is φ = 14108640.

The previous prime is 21216053. The next prime is 21216061. The reversal of 21216057 is 75061212.

It is an interprime number because it is at equal distance from previous prime (21216053) and next prime (21216061).

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

It is not a de Polignac number, because 21216057 - 2² = 21216053 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21216053) 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, 7419 + ... + 9872.

It is an arithmetic number, because the mean of its divisors is an integer number (3544860).

Almost surely, 2^21216057 is an apocalyptic number.

It is an amenable number.

21216057 is a deficient number, since it is larger than the sum of its proper divisors (7142823).

21216057 is a wasteful number, since it uses less digits than its factorization.

21216057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17703.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21216057 is about 4606.0891220210. The cubic root of 21216057 is about 276.8353576808.

Adding to 21216057 its reverse (75061212), we get a palindrome (96277269).

The spelling of 21216057 in words is "twenty-one million, two hundred sixteen thousand, fifty-seven".