42123721 has 2 divisors, whose sum is σ = 42123722. Its totient is φ = 42123720.

The previous prime is 42123691. The next prime is 42123727. The reversal of 42123721 is 12732124.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37650496 + 4473225 = 6136^2 + 2115^2 .

It is a cyclic number.

It is not a de Polignac number, because 42123721 - 2⁷ = 42123593 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 42123692 and 42123701.

It is not a weakly prime, because it can be changed into another prime (42123727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21061860 + 21061861.

It is an arithmetic number, because the mean of its divisors is an integer number (21061861).

Almost surely, 2^42123721 is an apocalyptic number.

It is an amenable number.

42123721 is a deficient number, since it is larger than the sum of its proper divisors (1).

42123721 is an equidigital number, since it uses as much as digits as its factorization.

42123721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 672, while the sum is 22.

The square root of 42123721 is about 6490.2789616472. The cubic root of 42123721 is about 347.9436453643.

Adding to 42123721 its reverse (12732124), we get a palindrome (54855845).

It can be divided in two parts, 421 and 23721, that added together give a palindrome (24142).

The spelling of 42123721 in words is "forty-two million, one hundred twenty-three thousand, seven hundred twenty-one".