61721551 has 4 divisors (see below), whose sum is σ = 61758400. Its totient is φ = 61684704.

The previous prime is 61721549. The next prime is 61721563. The reversal of 61721551 is 15512716.

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

It is a cyclic number.

It is not a de Polignac number, because 61721551 - 2¹ = 61721549 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 (61721501) 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, 15786 + ... + 19303.

It is an arithmetic number, because the mean of its divisors is an integer number (15439600).

Almost surely, 2^61721551 is an apocalyptic number.

61721551 is a deficient number, since it is larger than the sum of its proper divisors (36849).

61721551 is a wasteful number, since it uses less digits than its factorization.

61721551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36848.

The product of its digits is 2100, while the sum is 28.

The square root of 61721551 is about 7856.3064476890. The cubic root of 61721551 is about 395.1957604673.

The spelling of 61721551 in words is "sixty-one million, seven hundred twenty-one thousand, five hundred fifty-one".