42151721 has 4 divisors (see below), whose sum is σ = 44631252. Its totient is φ = 39672192.

The previous prime is 42151699. The next prime is 42151729. The reversal of 42151721 is 12715124.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38688400 + 3463321 = 6220^2 + 1861^2 .

It is a cyclic number.

It is not a de Polignac number, because 42151721 - 2⁶ = 42151657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (42151729) 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, 1239740 + ... + 1239773.

It is an arithmetic number, because the mean of its divisors is an integer number (11157813).

Almost surely, 2^42151721 is an apocalyptic number.

It is an amenable number.

42151721 is a deficient number, since it is larger than the sum of its proper divisors (2479531).

42151721 is a wasteful number, since it uses less digits than its factorization.

42151721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2479530.

The product of its digits is 560, while the sum is 23.

The square root of 42151721 is about 6492.4356754611. The cubic root of 42151721 is about 348.0207220012.

Adding to 42151721 its reverse (12715124), we get a palindrome (54866845).

The spelling of 42151721 in words is "forty-two million, one hundred fifty-one thousand, seven hundred twenty-one".