100020721 has 4 divisors (see below), whose sum is σ = 104369472. Its totient is φ = 95671972.

The previous prime is 100020703. The next prime is 100020733. The reversal of 100020721 is 127020001.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 100020721 - 2¹⁹ = 99496433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (100020761) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2174341 + ... + 2174386.

It is an arithmetic number, because the mean of its divisors is an integer number (26092368).

Almost surely, 2^100020721 is an apocalyptic number.

It is an amenable number.

100020721 is a deficient number, since it is larger than the sum of its proper divisors (4348751).

100020721 is an equidigital number, since it uses as much as digits as its factorization.

100020721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4348750.

The product of its (nonzero) digits is 28, while the sum is 13.

The square root of 100020721 is about 10001.0359963356. The cubic root of 100020721 is about 464.1909406013.

Adding to 100020721 its reverse (127020001), we get a palindrome (227040722).

The spelling of 100020721 in words is "one hundred million, twenty thousand, seven hundred twenty-one".