1251721969 has 4 divisors (see below), whose sum is σ = 1257335296. Its totient is φ = 1246108644.

The previous prime is 1251721967. The next prime is 1251721997. The reversal of 1251721969 is 9691271521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1251721969 - 2¹ = 1251721967 is a prime.

It is a super-2 number, since 2×1251721969² = 3133615775354473922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1251721963) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2806329 + ... + 2806774.

It is an arithmetic number, because the mean of its divisors is an integer number (314333824).

Almost surely, 2^1251721969 is an apocalyptic number.

It is an amenable number.

1251721969 is a deficient number, since it is larger than the sum of its proper divisors (5613327).

1251721969 is an equidigital number, since it uses as much as digits as its factorization.

1251721969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5613326.

The product of its digits is 68040, while the sum is 43.

The square root of 1251721969 is about 35379.6829974493. The cubic root of 1251721969 is about 1077.7117673506.

The spelling of 1251721969 in words is "one billion, two hundred fifty-one million, seven hundred twenty-one thousand, nine hundred sixty-nine".