42721909 has 4 divisors (see below), whose sum is σ = 42755904. Its totient is φ = 42687916.

The previous prime is 42721891. The next prime is 42721927. The reversal of 42721909 is 90912724.

It is a happy number.

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 an interprime number because it is at equal distance from previous prime (42721891) and next prime (42721927).

It is a cyclic number.

It is not a de Polignac number, because 42721909 - 2¹³ = 42713717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42721949) 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, 15037 + ... + 17650.

It is an arithmetic number, because the mean of its divisors is an integer number (10688976).

Almost surely, 2^42721909 is an apocalyptic number.

It is an amenable number.

42721909 is a deficient number, since it is larger than the sum of its proper divisors (33995).

42721909 is a wasteful number, since it uses less digits than its factorization.

42721909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33994.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 42721909 is about 6536.1998898443. The cubic root of 42721909 is about 349.5829290530.

The spelling of 42721909 in words is "forty-two million, seven hundred twenty-one thousand, nine hundred nine".