61521457621 has 4 divisors (see below), whose sum is σ = 66253877452. Its totient is φ = 56789037792.

The previous prime is 61521457603. The next prime is 61521457693. The reversal of 61521457621 is 12675412516.

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 6571534225 + 54949923396 = 81065^2 + 234414^2 .

It is a cyclic number.

It is not a de Polignac number, because 61521457621 - 2¹⁹ = 61520933333 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 (61521457321) 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, 2366209896 + ... + 2366209921.

It is an arithmetic number, because the mean of its divisors is an integer number (16563469363).

Almost surely, 2^61521457621 is an apocalyptic number.

It is an amenable number.

61521457621 is a deficient number, since it is larger than the sum of its proper divisors (4732419831).

61521457621 is a wasteful number, since it uses less digits than its factorization.

61521457621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4732419830.

The product of its digits is 100800, while the sum is 40.

The spelling of 61521457621 in words is "sixty-one billion, five hundred twenty-one million, four hundred fifty-seven thousand, six hundred twenty-one".