20721057 has 8 divisors (see below), whose sum is σ = 31574976. Its totient is φ = 11840592.

The previous prime is 20721053. The next prime is 20721083. The reversal of 20721057 is 75012702.

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

It is not a de Polignac number, because 20721057 - 2² = 20721053 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20721053) 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, 493338 + ... + 493379.

It is an arithmetic number, because the mean of its divisors is an integer number (3946872).

Almost surely, 2^20721057 is an apocalyptic number.

It is an amenable number.

20721057 is a deficient number, since it is larger than the sum of its proper divisors (10853919).

20721057 is an equidigital number, since it uses as much as digits as its factorization.

20721057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986727.

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 20721057 is about 4552.0387740001. The cubic root of 20721057 is about 274.6654090481.

Adding to 20721057 its reverse (75012702), we get a palindrome (95733759).

The spelling of 20721057 in words is "twenty million, seven hundred twenty-one thousand, fifty-seven".