61815251 has 4 divisors (see below), whose sum is σ = 62129232. Its totient is φ = 61501272.

The previous prime is 61815239. The next prime is 61815253. The reversal of 61815251 is 15251816.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61815251 is a prime.

It is a super-2 number, since 2×61815251² = 7642250512386002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61815253) 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, 156695 + ... + 157088.

It is an arithmetic number, because the mean of its divisors is an integer number (15532308).

Almost surely, 2^61815251 is an apocalyptic number.

61815251 is a deficient number, since it is larger than the sum of its proper divisors (313981).

61815251 is a wasteful number, since it uses less digits than its factorization.

61815251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 313980.

The product of its digits is 2400, while the sum is 29.

The square root of 61815251 is about 7862.2675482331. The cubic root of 61815251 is about 395.3956426776.

The spelling of 61815251 in words is "sixty-one million, eight hundred fifteen thousand, two hundred fifty-one".