15721001 has 4 divisors (see below), whose sum is σ = 15762432. Its totient is φ = 15679572.

The previous prime is 15720989. The next prime is 15721003. The reversal of 15721001 is 10012751.

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 15721001 - 2¹⁸ = 15458857 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (15721003) 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, 20141 + ... + 20906.

It is an arithmetic number, because the mean of its divisors is an integer number (3940608).

Almost surely, 2^15721001 is an apocalyptic number.

It is an amenable number.

15721001 is a deficient number, since it is larger than the sum of its proper divisors (41431).

15721001 is an equidigital number, since it uses as much as digits as its factorization.

15721001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41430.

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 15721001 is about 3964.9717527367. The cubic root of 15721001 is about 250.5109603001.

Adding to 15721001 its reverse (10012751), we get a palindrome (25733752).

The spelling of 15721001 in words is "fifteen million, seven hundred twenty-one thousand, one".