1621921757381 has 4 divisors (see below), whose sum is σ = 1622012981472. Its totient is φ = 1621830533292.

The previous prime is 1621921757363. The next prime is 1621921757387. The reversal of 1621921757381 is 1837571291261.

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 1621921757381 - 2³⁰ = 1620848015557 is a prime.

It is a super-2 number, since 2×1621921757381² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621921757387) 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, 45585371 + ... + 45620936.

It is an arithmetic number, because the mean of its divisors is an integer number (405503245368).

Almost surely, 2^{1621921757381} is an apocalyptic number.

It is an amenable number.

1621921757381 is a deficient number, since it is larger than the sum of its proper divisors (91224091).

1621921757381 is an equidigital number, since it uses as much as digits as its factorization.

1621921757381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91224090.

The product of its digits is 1270080, while the sum is 53.

The spelling of 1621921757381 in words is "one trillion, six hundred twenty-one billion, nine hundred twenty-one million, seven hundred fifty-seven thousand, three hundred eighty-one".