1561621501 has 32 divisors (see below), whose sum is σ = 1811496960. Its totient is φ = 1332355200.

The previous prime is 1561621441. The next prime is 1561621517. The reversal of 1561621501 is 1051261651.

It is a happy number.

It is not a de Polignac number, because 1561621501 - 2⁹ = 1561620989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1561621501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561621301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5021136 + ... + 5021446.

It is an arithmetic number, because the mean of its divisors is an integer number (56609280).

Almost surely, 2^1561621501 is an apocalyptic number.

1561621501 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1561621501 is a deficient number, since it is larger than the sum of its proper divisors (249875459).

1561621501 is a wasteful number, since it uses less digits than its factorization.

1561621501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 657.

The product of its (nonzero) digits is 1800, while the sum is 28.

The square root of 1561621501 is about 39517.3569586834. The cubic root of 1561621501 is about 1160.1796939718.

The spelling of 1561621501 in words is "one billion, five hundred sixty-one million, six hundred twenty-one thousand, five hundred one".