61721021 has 4 divisors (see below), whose sum is σ = 62767200. Its totient is φ = 60674844.

The previous prime is 61721017. The next prime is 61721027. The reversal of 61721021 is 12012716.

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 61721021 - 2² = 61721017 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 61720984 and 61721002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61721027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 523001 + ... + 523118.

It is an arithmetic number, because the mean of its divisors is an integer number (15691800).

Almost surely, 2^61721021 is an apocalyptic number.

It is an amenable number.

61721021 is a deficient number, since it is larger than the sum of its proper divisors (1046179).

61721021 is a wasteful number, since it uses less digits than its factorization.

61721021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1046178.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 61721021 is about 7856.2727167532. The cubic root of 61721021 is about 395.1946292884.

Adding to 61721021 its reverse (12012716), we get a palindrome (73733737).

The spelling of 61721021 in words is "sixty-one million, seven hundred twenty-one thousand, twenty-one".