1972921921 has 4 divisors (see below), whose sum is σ = 1973356992. Its totient is φ = 1972486852.

The previous prime is 1972921919. The next prime is 1972921931. The reversal of 1972921921 is 1291292791.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1291292791 = 33769 ⋅38239.

It is a cyclic number.

It is not a de Polignac number, because 1972921921 - 2¹ = 1972921919 is a prime.

It is a super-3 number, since 3×1972921921³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1972921931) 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, 210661 + ... + 219826.

It is an arithmetic number, because the mean of its divisors is an integer number (493339248).

Almost surely, 2^1972921921 is an apocalyptic number.

It is an amenable number.

1972921921 is a deficient number, since it is larger than the sum of its proper divisors (435071).

1972921921 is an equidigital number, since it uses as much as digits as its factorization.

1972921921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 435070.

The product of its digits is 40824, while the sum is 43.

The square root of 1972921921 is about 44417.5857178213. The cubic root of 1972921921 is about 1254.2091536580.

The spelling of 1972921921 in words is "one billion, nine hundred seventy-two million, nine hundred twenty-one thousand, nine hundred twenty-one".