1291551921 has 24 divisors (see below), whose sum is σ = 2039697504. Its totient is φ = 781018560.

The previous prime is 1291551893. The next prime is 1291551929.

1291551921 is a `hidden beast` number, since 12 + 9 + 1 + 551 + 92 + 1 = 666.

1291551921 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1291551921 - 2⁶ = 1291551857 is a prime.

It is a super-3 number, since 3×1291551921³ (a number of 28 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (1291551929) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30970 + ... + 59516.

It is an arithmetic number, because the mean of its divisors is an integer number (84987396).

Almost surely, 2^1291551921 is an apocalyptic number.

1291551921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1291551921 is a deficient number, since it is larger than the sum of its proper divisors (748145583).

1291551921 is a wasteful number, since it uses less digits than its factorization.

1291551921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29021 (or 29018 counting only the distinct ones).

The product of its digits is 8100, while the sum is 36.

The square root of 1291551921 is about 35938.1680250955. The cubic root of 1291551921 is about 1089.0235963388.

The spelling of 1291551921 in words is "one billion, two hundred ninety-one million, five hundred fifty-one thousand, nine hundred twenty-one".