1561221651 has 16 divisors (see below), whose sum is σ = 2282404608. Its totient is φ = 941388000.

The previous prime is 1561221637. The next prime is 1561221653.

1561221651 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1561221651 - 2¹⁵ = 1561188883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1561221653) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 113575 + ... + 126576.

It is an arithmetic number, because the mean of its divisors is an integer number (142650288).

Almost surely, 2^1561221651 is an apocalyptic number.

1561221651 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1561221651 is a deficient number, since it is larger than the sum of its proper divisors (721182957).

1561221651 is a wasteful number, since it uses less digits than its factorization.

1561221651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240362.

The product of its digits is 3600, while the sum is 30.

The square root of 1561221651 is about 39512.2974654727. The cubic root of 1561221651 is about 1160.0806649712.

The spelling of 1561221651 in words is "one billion, five hundred sixty-one million, two hundred twenty-one thousand, six hundred fifty-one".