1261551621 has 8 divisors (see below), whose sum is σ = 1834984224. Its totient is φ = 764576720.

The previous prime is 1261551601. The next prime is 1261551631.

1261551621 is nontrivially palindromic in base 10.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1261551621 - 2¹⁴ = 1261535237 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261551601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19114386 + ... + 19114451.

It is an arithmetic number, because the mean of its divisors is an integer number (229373028).

Almost surely, 2^1261551621 is an apocalyptic number.

1261551621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1261551621 is a deficient number, since it is larger than the sum of its proper divisors (573432603).

1261551621 is a wasteful number, since it uses less digits than its factorization.

1261551621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38228851.

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

The square root of 1261551621 is about 35518.3279589566. The cubic root of 1261551621 is about 1080.5254704586.

The spelling of 1261551621 in words is "one billion, two hundred sixty-one million, five hundred fifty-one thousand, six hundred twenty-one".