1221755216621 has 16 divisors (see below), whose sum is σ = 1302684954624. Its totient is φ = 1143169137264.

The previous prime is 1221755216611. The next prime is 1221755216639. The reversal of 1221755216621 is 1266125571221.

It is a de Polignac number, because none of the positive numbers 2^k-1221755216621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221755216611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1765136 + ... + 2357798.

It is an arithmetic number, because the mean of its divisors is an integer number (81417809664).

Almost surely, 2^{1221755216621} is an apocalyptic number.

It is an amenable number.

1221755216621 is a deficient number, since it is larger than the sum of its proper divisors (80929738003).

1221755216621 is a wasteful number, since it uses less digits than its factorization.

1221755216621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594640.

The product of its digits is 100800, while the sum is 41.

The spelling of 1221755216621 in words is "one trillion, two hundred twenty-one billion, seven hundred fifty-five million, two hundred sixteen thousand, six hundred twenty-one".