1621611441561 has 4 divisors (see below), whose sum is σ = 2162148588752. Its totient is φ = 1081074294372.

The previous prime is 1621611441547. The next prime is 1621611441631. The reversal of 1621611441561 is 1651441161261.

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 not a de Polignac number, because 1621611441561 - 2⁶ = 1621611441497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621611441521) 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, 270268573591 + ... + 270268573596.

It is an arithmetic number, because the mean of its divisors is an integer number (540537147188).

Almost surely, 2^{1621611441561} is an apocalyptic number.

It is an amenable number.

1621611441561 is a deficient number, since it is larger than the sum of its proper divisors (540537147191).

1621611441561 is an equidigital number, since it uses as much as digits as its factorization.

1621611441561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540537147190.

The product of its digits is 34560, while the sum is 39.

The spelling of 1621611441561 in words is "one trillion, six hundred twenty-one billion, six hundred eleven million, four hundred forty-one thousand, five hundred sixty-one".