1721121257551 has 8 divisors (see below), whose sum is σ = 1761167764224. Its totient is φ = 1681075679640.

The previous prime is 1721121257507. The next prime is 1721121257561. The reversal of 1721121257551 is 1557521211271.

It is a happy number.

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 1721121257551 - 2⁷ = 1721121257423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721121257501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4742970 + ... + 5092936.

It is an arithmetic number, because the mean of its divisors is an integer number (220145970528).

Almost surely, 2^{1721121257551} is an apocalyptic number.

1721121257551 is a deficient number, since it is larger than the sum of its proper divisors (40046506673).

1721121257551 is a wasteful number, since it uses less digits than its factorization.

1721121257551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 464381.

The product of its digits is 49000, while the sum is 40.

The spelling of 1721121257551 in words is "one trillion, seven hundred twenty-one billion, one hundred twenty-one million, two hundred fifty-seven thousand, five hundred fifty-one".